# EDGAR Filing Document

**Accession Number:** 0001447362
**File Stem:** 0001628280-26-012280
**Filing Date:** 2026-2
**Character Count:** 43070
**Document Hash:** e0c3c4fd0202480988bd4557c34d9cde
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001628280-26-012280.hdr.sgml**: 20260226

**ACCESSION NUMBER**: 0001628280-26-012280

**CONFORMED SUBMISSION TYPE**: S-8

**PUBLIC DOCUMENT COUNT**: 15

**FILED AS OF DATE**: 20260226

**DATE AS OF CHANGE**: 20260226

**EFFECTIVENESS DATE**: 20260226

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** CASTLE BIOSCIENCES INC
- **CENTRAL INDEX KEY:** 0001447362
- **STANDARD INDUSTRIAL CLASSIFICATION:** SERVICES-MEDICAL LABORATORIES [8071]
- **ORGANIZATION NAME:** 08 Industrial Applications and Services
- **EIN:** 770701774
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** S-8
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 333-293790
- **FILM NUMBER:** 26688204

**BUSINESS ADDRESS:**
- **STREET 1:** 1500 W. PARKWOOD AVE.
- **STREET 2:** SUITE 400
- **CITY:** FRIENDSWOOD
- **STATE:** TX
- **ZIP:** 77546
- **BUSINESS PHONE:** 866-788-9007

**MAIL ADDRESS:**
- **STREET 1:** 1500 W. PARKWOOD AVE.
- **STREET 2:** SUITE 400
- **CITY:** FRIENDSWOOD
- **STATE:** TX
- **ZIP:** 77546

**As filed with the Securities and Exchange Commission on February 26, 2026** 

**Registration No. 333-** 

    

**UNITED STATES** 

**SECURITIES AND EXCHANGE COMMISSION** 

**Washington, D.C. 20549** 

**FORM S-8** 

**REGISTRATION STATEMENT** 

***UNDER***

***THE SECURITIES ACT OF 1933***

**Castle Biosciences, Inc.** 

**(Exact name of registrant as specified in its charter)** 

---

| | |
|:---|:---|
| **Delaware** | **77-0701774** |
| **(State or other jurisdiction of**<br>**incorporation or organization)** | **(I.R.S. Employer**<br>**Identification No.)** |
| **1500 W. Parkwood Ave, Suite 400**<br>**Friendswood, Texas** | **77546** |
| **(Address of Principal Executive Offices)** | **(Zip Code)** |

---

<br>**Castle Biosciences, Inc. 2019 Equity Incentive Plan**

**Castle Biosciences, Inc. 2019 Employee Stock Purchase Plan** 

**(Full titles of the plans)** 

**Derek J. Maetzold** 

**President and Chief Executive Officer** 

**Castle Biosciences, Inc.** 

**1500 W. Parkwood Ave, Suite 400**

**Friendswood, Texas 77546** 

**(866) 788-9907** 

**(Name, address, including zip code, and telephone number, including area code, of agent for service)** 

***Copies to:***

**Thomas A. Coll, Esq.**<br>**Carlos Ramirez, Esq.**<br>**Cooley LLP**<br>**10265 Science Center Drive**<br>**San Diego, California 92121**<br>**(858) 550-6000**<br>

Indicate by check mark whether the Registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of "large accelerated filer," "accelerated filer," "smaller reporting company," and "emerging growth company" in Rule 12b-2 of the Exchange Act.

---

| | | | |
|:---|:---|:---|:---|
| Large accelerated filer | □ | Accelerated filer | ⌧ |
| Non-accelerated filer | □ | Smaller reporting company | □ |
| Emerging growth company | □ | | |

---

If an emerging growth company, indicate by check mark if the Registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. □

------

**EXPLANATORY NOTE**

This Registration Statement on Form S-8 is being filed by Castle Biosciences, Inc. (the "***Registrant***") for the purpose of registering (i) an additional 1,484,315 shares of the Registrant's Common Stock, $0.001 par value per share ("***Common Stock***"), under the Registrant's 2019 Equity Incentive Plan (the "***2019 Plan***"), pursuant to the provisions of the 2019 Plan providing for an automatic increase in the number of shares of Common Stock reserved and available for issuance under the 2019 Plan, and (ii) 296,863 additional shares of Common Stock under the Registrant's 2019 Employee Stock Purchase Plan (the "***2019 ESPP***") pursuant to the provisions of the 2019 ESPP providing for an automatic increase in the number of shares of Common Stock reserved and available for issuance under the 2019 ESPP, in each case on January 1, 2026.

**INCORPORATION OF DOCUMENTS BY REFERENCE** 

This Registration Statement is being filed for the purpose of registering additional securities of the same class as other securities for which Registration Statements of the Registrant on Form S-8 relating to the same employee benefit plans are effective.

The Registrant previously registered shares of its Common Stock for issuance under the 2019 Plan and 2019 ESPP under Registration Statements on Form S-8 filed with the Securities and Exchange Commission (the "***SEC***") on <u>[July 29, 2019 (File No. 333-232884)](https://www.sec.gov/Archives/edgar/data/1447362/000114036119013647/nt10003552x1_s8.htm)</u>, <u>[March 10, 2020 (File No. 333-237062)](https://www.sec.gov/Archives/edgar/data/1447362/000144736220000030/forms-8x2019equityincentiv.htm)</u>, <u>[March 11, 2021 (File No. 333-254179)](https://www.sec.gov/Archives/edgar/data/1447362/000144736221000049/forms-8x2019equityincentiv.htm)</u>, <u>[February 28, 2022 (File No. 333-263094)](https://www.sec.gov/Archives/edgar/data/1447362/000144736222000046/forms-8x2019equityincentiv.htm)</u>, <u>[February 28, 2023 (File No. 333-270141)](https://www.sec.gov/Archives/edgar/data/1447362/000144736223000039/forms-8x2019equityincentiv.htm)</u>, <u>[February 28, 2024 (File No. 333-277472)](https://www.sec.gov/Archives/edgar/data/1447362/000119312524050892/d736549ds8.htm)</u> and <u>[February 27](https://www.sec.gov/Archives/edgar/data/1447362/000144736225000032/forms-8x2019equityincentiv.htm)[, 2025 (File No. 333-285331)](https://www.sec.gov/Archives/edgar/data/1447362/000144736225000032/forms-8x2019equityincentiv.htm)</u>. Pursuant to General Instruction E to Form S-8, this Registration Statement hereby incorporates by reference the contents of the Registration Statements referenced above.

------

**ITEM 8. EXHIBITS.** 

---

| | |
|:---|:---|
| **Exhibit Number** | &nbsp;&nbsp;**Description** |
| 4.1 | <u>[Amended and Restated Certificate of Incorporation of the Registrant, incorporated by reference to Exhibit 3.1 to the Registrant's Current Report on Form 8-K, filed with the SEC on May 23, 2025.](https://www.sec.gov/Archives/edgar/data/1447362/000144736225000085/exhibit-31.htm)</u> |
| 4.2 | <u>[Amended and Restated Bylaws of the Registrant, incorporated by reference to Exhibit 3.](https://www.sec.gov/Archives/edgar/data/1447362/000144736225000099/exhibit31-castlexamendedan.htm)[1](https://www.sec.gov/Archives/edgar/data/1447362/000144736225000099/exhibit31-castlexamendedan.htm)[to the Registrant's Current Report on Form 8-K, filed with the SEC on August 8, 2025.](https://www.sec.gov/Archives/edgar/data/1447362/000144736225000099/exhibit31-castlexamendedan.htm)</u> |
| 4.3 | <u>[Form of Common Stock Certificate of the Registrant. incorporated by reference to Exhibit 4.1 to the Registrant's Registration Statement on Form S-1 (File No. 333-232369), originally filed with the SEC on June 26, 2019, as amended.](https://www.sec.gov/Archives/edgar/data/1447362/000114036119012901/nt10000802x4_ex4-1.htm)</u> |
| 5.1\* | <u>[Opinion of Cooley LLP.](exhibit51-opinionofcooleyf.htm)</u> |
| 23.1\* | <u>[Consent of KPMG LLP, Independent Registered Public Accounting Firm.](ex231-kpmgsx8opinionfebrua.htm)</u> |
| 23.2\* | <u>[Consent of Cooley LLP. Reference is made to Exhibit 5.1.](exhibit51-opinionofcooleyf.htm)</u> |
| 24.1\* | <u>[Power of Attorney. Reference is made to the signature page hereto.](#i32bee36d6e894acd93ea883f97e2ad23_4)</u> |
| 99.1 | <u>[Castle Biosciences, Inc. 2019 Equity Incentive Plan, incorporated by reference to Exhibit 99.3 to the Registrant's Registration Statement on Form S-8 (File No. 333-232884), filed with the SEC on July 29, 2019.](https://www.sec.gov/Archives/edgar/data/1447362/000114036119013647/nt10003552x1_ex99-3.htm)</u> |
| 99.2 | <u>[Forms of Stock Option Grant Notice, Option Agreement and Notice of Exercise under the 2019 Plan, incorporated by reference to Exhibit 10.7 to the Registrant's Registration Statement on Form S-1 (File No. 333-232369), as amended, originally filed with the SEC on June 26, 2019.](https://www.sec.gov/Archives/edgar/data/1447362/000114036119011686/nt10000802x2_ex10-7.htm)</u> |
| 99.3 | <u>[Forms of Restricted Stock Unit Grant Notice and Restricted Stock Unit Award Agreement under the 2019 Equity Incentive Plan, incorporated by reference to Exhibit 10.1 to the Registrant's Quarterly Report on Form 10-Q, filed with SEC on November 9, 2020.](https://www.sec.gov/Archives/edgar/data/1447362/000144736220000257/exhibit101-q32020.htm)</u> |
| 99.4 | <u>[Castle Biosciences, Inc. 2019 Employee Stock Purchase Plan, incorporated by reference to Exhibit 10.8 to the Registrant's Registration Statement on Form S-1 (File No. 333-232369), as amended, originally filed with the SEC on June 26, 2019.](https://www.sec.gov/Archives/edgar/data/1447362/000114036119012901/nt10000802x4_ex10-8.htm)</u> |
| 107\* | <u>[Filing Fee Table](exfilingfees.htm)</u> |

---

__________________________________

\*&nbsp;&nbsp;&nbsp;&nbsp;Filed herewith.

------

**SIGNATURES**

Pursuant to the requirements of the Securities Act of 1933, as amended, the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Friendswood, State of Texas, on February 26, 2026.

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp;**CASTLE BIOSCIENCES, INC.** | &nbsp;&nbsp;&nbsp;**CASTLE BIOSCIENCES, INC.** |
| &nbsp;&nbsp;&nbsp;By: | &nbsp;&nbsp;&nbsp;/s/ Derek J. Maetzold |
|  | &nbsp;&nbsp;&nbsp;Derek J. Maetzold |
|  | &nbsp;&nbsp;&nbsp;*President and Chief Executive Officer* |

---

**POWER OF ATTORNEY** 

KNOW ALL BY THESE PRESENTS, that each person whose signature appears below constitutes and appoints Derek J. Maetzold and Frank Stokes, and each of them, as his or her true and lawful attorneys-in-fact and agents, each with the full power of substitution, for him or her and in his or her name, place or stead, in any and all capacities, to sign any and all amendments to this Registration Statement (including post-effective amendments), and to file the same, with exhibits thereto and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as he or she might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents, or their substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1933, as amended, this Registration Statement has been signed by the following persons in the capacities and on the dates indicated.

------

---

| | | |
|:---|:---|:---|
| **Signature** | **Title** | **Date** |
| /s/ Derek J. Maetzold | President, Chief Executive Officer and Director | February 26, 2026 |
| Derek J. Maetzold | *(Principal Executive Officer)* |  |
| /s/ Frank Stokes | Chief Financial Officer | February 26, 2026 |
| Frank Stokes | *(Principal Financial and Accounting Officer)* |  |
| /s/ Daniel M. Bradbury | Chairperson of the Board of Directors | February 26, 2026 |
| Daniel M. Bradbury |  |  |
| /s/ Kimberlee S. Caple | Member of the Board of Directors | February 26, 2026 |
| Kimberlee S. Caple |  |  |
| /s/ G. Bradley Cole | Member of the Board of Directors | February 26, 2026 |
| G. Bradley Cole |  |  |
| /s/ Rodney Cotton | Member of the Board of Directors | February 26, 2026 |
| Rodney Cotton |  |  |
| /s/ Ellen Goldberg | Member of the Board of Directors | February 26, 2026 |
| Ellen Goldberg |  |  |
| /s/ Miles D. Harrison | Member of the Board of Directors | February 26, 2026 |
| Miles D. Harrison |  |  |
| /s/ Tiffany P. Olson | Member of the Board of Directors | February 26, 2026 |
| Tiffany P. Olson |  |  |

---

## Ex-Filing

?xml version='1.0' encoding='ASCII'? exfilingfees

**Exhibit 107**

**Calculation of Filing Fee Table**

**Form S-8**

**Castle Biosciences, Inc.**

<u>Table 1: Newly Registered Securities</u>

---

| | | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|:---|
| | **Security Type** | **Security<br>Class<br>Title** | **Fee Calculation Rule** | **Amount Registered** | **Proposed Maximum Offering Price Per Unit** | **Maximum Aggregate Offering Price** | **Fee<br>Rate** | **Amount of Registration Fee** |
| 1 | Equity | 2019 Equity Incentive Plan, Common Stock, $0.001 per share | Other | 1484315 | $32.31 | $47958217.65 | $0.0001381 | $6623.03 |
| 2 | Equity | 2019 Employee Stock Incentive Plan, Common Stock, $0.001 per share | Other | 296863 | $27.46 | $8151857.98 | $0.0001381 | $1125.77 |
| Total Offering Amounts: | Total Offering Amounts: | Total Offering Amounts: | Total Offering Amounts: | Total Offering Amounts: |  | $56110075.63 |  | $7748.80 |
| Total Fee Offsets: | Total Fee Offsets: | Total Fee Offsets: | Total Fee Offsets: | Total Fee Offsets: |  |  |  | $0.00 |
| Net Fee Due: | Net Fee Due: | Net Fee Due: | Net Fee Due: | Net Fee Due: |  |  |  | $7748.80 |
| Offering Note | Offering Note | Offering Note | Offering Note | Offering Note | Offering Note | Offering Note | Offering Note | Offering Note |
| 1 | Pursuant to Rule 416(a) under the Securities Act of 1933, as amended (the "Securities Act"), this Registration Statement on Form S-8 (this "Registration Statement") shall also cover any additional shares of Common Stock, par value $0.001 per share ("Common Stock") of Castle Biosciences, Inc. (the "Registrant") that become issuable under the Registrant's 2019 Equity Incentive Plan (the "2019 Plan") by reason of any stock dividend, stock split, recapitalization or other similar transaction. Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rules 457(c) and 457(h)(1) of the Securities Act. The proposed maximum aggregate offering price per unit and proposed maximum aggregate offering price are calculated using the average of the high and low prices of the Common Stock as reported on the Nasdaq Global Market on February 19, 2026 (the "Average Price"), which date is within five business days prior to the filing of this Registration Statement. Represents shares of Common Stock that were automatically added to the shares authorized for issuance under the 2019 Plan on January 1, 2026 pursuant to an "evergreen" provision contained in the 2019 Plan. Pursuant to such provision, on January 1st of each year through (and including) January 1, 2029, the number of shares authorized for issuance under the 2019 Plan will be automatically increased by an amount equal to the lesser of: (a) 5% of the total number of shares of capital stock of the Registrant outstanding on December 31 of the preceding calendar year; or (b) such lesser number of shares of Common Stock as the Registrant's board of directors (the "Board") may designate prior to the applicable January 1st. | Pursuant to Rule 416(a) under the Securities Act of 1933, as amended (the "Securities Act"), this Registration Statement on Form S-8 (this "Registration Statement") shall also cover any additional shares of Common Stock, par value $0.001 per share ("Common Stock") of Castle Biosciences, Inc. (the "Registrant") that become issuable under the Registrant's 2019 Equity Incentive Plan (the "2019 Plan") by reason of any stock dividend, stock split, recapitalization or other similar transaction. Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rules 457(c) and 457(h)(1) of the Securities Act. The proposed maximum aggregate offering price per unit and proposed maximum aggregate offering price are calculated using the average of the high and low prices of the Common Stock as reported on the Nasdaq Global Market on February 19, 2026 (the "Average Price"), which date is within five business days prior to the filing of this Registration Statement. Represents shares of Common Stock that were automatically added to the shares authorized for issuance under the 2019 Plan on January 1, 2026 pursuant to an "evergreen" provision contained in the 2019 Plan. Pursuant to such provision, on January 1st of each year through (and including) January 1, 2029, the number of shares authorized for issuance under the 2019 Plan will be automatically increased by an amount equal to the lesser of: (a) 5% of the total number of shares of capital stock of the Registrant outstanding on December 31 of the preceding calendar year; or (b) such lesser number of shares of Common Stock as the Registrant's board of directors (the "Board") may designate prior to the applicable January 1st. | Pursuant to Rule 416(a) under the Securities Act of 1933, as amended (the "Securities Act"), this Registration Statement on Form S-8 (this "Registration Statement") shall also cover any additional shares of Common Stock, par value $0.001 per share ("Common Stock") of Castle Biosciences, Inc. (the "Registrant") that become issuable under the Registrant's 2019 Equity Incentive Plan (the "2019 Plan") by reason of any stock dividend, stock split, recapitalization or other similar transaction. Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rules 457(c) and 457(h)(1) of the Securities Act. The proposed maximum aggregate offering price per unit and proposed maximum aggregate offering price are calculated using the average of the high and low prices of the Common Stock as reported on the Nasdaq Global Market on February 19, 2026 (the "Average Price"), which date is within five business days prior to the filing of this Registration Statement. Represents shares of Common Stock that were automatically added to the shares authorized for issuance under the 2019 Plan on January 1, 2026 pursuant to an "evergreen" provision contained in the 2019 Plan. Pursuant to such provision, on January 1st of each year through (and including) January 1, 2029, the number of shares authorized for issuance under the 2019 Plan will be automatically increased by an amount equal to the lesser of: (a) 5% of the total number of shares of capital stock of the Registrant outstanding on December 31 of the preceding calendar year; or (b) such lesser number of shares of Common Stock as the Registrant's board of directors (the "Board") may designate prior to the applicable January 1st. | Pursuant to Rule 416(a) under the Securities Act of 1933, as amended (the "Securities Act"), this Registration Statement on Form S-8 (this "Registration Statement") shall also cover any additional shares of Common Stock, par value $0.001 per share ("Common Stock") of Castle Biosciences, Inc. (the "Registrant") that become issuable under the Registrant's 2019 Equity Incentive Plan (the "2019 Plan") by reason of any stock dividend, stock split, recapitalization or other similar transaction. Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rules 457(c) and 457(h)(1) of the Securities Act. The proposed maximum aggregate offering price per unit and proposed maximum aggregate offering price are calculated using the average of the high and low prices of the Common Stock as reported on the Nasdaq Global Market on February 19, 2026 (the "Average Price"), which date is within five business days prior to the filing of this Registration Statement. Represents shares of Common Stock that were automatically added to the shares authorized for issuance under the 2019 Plan on January 1, 2026 pursuant to an "evergreen" provision contained in the 2019 Plan. Pursuant to such provision, on January 1st of each year through (and including) January 1, 2029, the number of shares authorized for issuance under the 2019 Plan will be automatically increased by an amount equal to the lesser of: (a) 5% of the total number of shares of capital stock of the Registrant outstanding on December 31 of the preceding calendar year; or (b) such lesser number of shares of Common Stock as the Registrant's board of directors (the "Board") may designate prior to the applicable January 1st. | Pursuant to Rule 416(a) under the Securities Act of 1933, as amended (the "Securities Act"), this Registration Statement on Form S-8 (this "Registration Statement") shall also cover any additional shares of Common Stock, par value $0.001 per share ("Common Stock") of Castle Biosciences, Inc. (the "Registrant") that become issuable under the Registrant's 2019 Equity Incentive Plan (the "2019 Plan") by reason of any stock dividend, stock split, recapitalization or other similar transaction. Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rules 457(c) and 457(h)(1) of the Securities Act. The proposed maximum aggregate offering price per unit and proposed maximum aggregate offering price are calculated using the average of the high and low prices of the Common Stock as reported on the Nasdaq Global Market on February 19, 2026 (the "Average Price"), which date is within five business days prior to the filing of this Registration Statement. Represents shares of Common Stock that were automatically added to the shares authorized for issuance under the 2019 Plan on January 1, 2026 pursuant to an "evergreen" provision contained in the 2019 Plan. Pursuant to such provision, on January 1st of each year through (and including) January 1, 2029, the number of shares authorized for issuance under the 2019 Plan will be automatically increased by an amount equal to the lesser of: (a) 5% of the total number of shares of capital stock of the Registrant outstanding on December 31 of the preceding calendar year; or (b) such lesser number of shares of Common Stock as the Registrant's board of directors (the "Board") may designate prior to the applicable January 1st. | Pursuant to Rule 416(a) under the Securities Act of 1933, as amended (the "Securities Act"), this Registration Statement on Form S-8 (this "Registration Statement") shall also cover any additional shares of Common Stock, par value $0.001 per share ("Common Stock") of Castle Biosciences, Inc. (the "Registrant") that become issuable under the Registrant's 2019 Equity Incentive Plan (the "2019 Plan") by reason of any stock dividend, stock split, recapitalization or other similar transaction. Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rules 457(c) and 457(h)(1) of the Securities Act. The proposed maximum aggregate offering price per unit and proposed maximum aggregate offering price are calculated using the average of the high and low prices of the Common Stock as reported on the Nasdaq Global Market on February 19, 2026 (the "Average Price"), which date is within five business days prior to the filing of this Registration Statement. Represents shares of Common Stock that were automatically added to the shares authorized for issuance under the 2019 Plan on January 1, 2026 pursuant to an "evergreen" provision contained in the 2019 Plan. Pursuant to such provision, on January 1st of each year through (and including) January 1, 2029, the number of shares authorized for issuance under the 2019 Plan will be automatically increased by an amount equal to the lesser of: (a) 5% of the total number of shares of capital stock of the Registrant outstanding on December 31 of the preceding calendar year; or (b) such lesser number of shares of Common Stock as the Registrant's board of directors (the "Board") may designate prior to the applicable January 1st. | Pursuant to Rule 416(a) under the Securities Act of 1933, as amended (the "Securities Act"), this Registration Statement on Form S-8 (this "Registration Statement") shall also cover any additional shares of Common Stock, par value $0.001 per share ("Common Stock") of Castle Biosciences, Inc. (the "Registrant") that become issuable under the Registrant's 2019 Equity Incentive Plan (the "2019 Plan") by reason of any stock dividend, stock split, recapitalization or other similar transaction. Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rules 457(c) and 457(h)(1) of the Securities Act. The proposed maximum aggregate offering price per unit and proposed maximum aggregate offering price are calculated using the average of the high and low prices of the Common Stock as reported on the Nasdaq Global Market on February 19, 2026 (the "Average Price"), which date is within five business days prior to the filing of this Registration Statement. Represents shares of Common Stock that were automatically added to the shares authorized for issuance under the 2019 Plan on January 1, 2026 pursuant to an "evergreen" provision contained in the 2019 Plan. Pursuant to such provision, on January 1st of each year through (and including) January 1, 2029, the number of shares authorized for issuance under the 2019 Plan will be automatically increased by an amount equal to the lesser of: (a) 5% of the total number of shares of capital stock of the Registrant outstanding on December 31 of the preceding calendar year; or (b) such lesser number of shares of Common Stock as the Registrant's board of directors (the "Board") may designate prior to the applicable January 1st. | Pursuant to Rule 416(a) under the Securities Act of 1933, as amended (the "Securities Act"), this Registration Statement on Form S-8 (this "Registration Statement") shall also cover any additional shares of Common Stock, par value $0.001 per share ("Common Stock") of Castle Biosciences, Inc. (the "Registrant") that become issuable under the Registrant's 2019 Equity Incentive Plan (the "2019 Plan") by reason of any stock dividend, stock split, recapitalization or other similar transaction. Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rules 457(c) and 457(h)(1) of the Securities Act. The proposed maximum aggregate offering price per unit and proposed maximum aggregate offering price are calculated using the average of the high and low prices of the Common Stock as reported on the Nasdaq Global Market on February 19, 2026 (the "Average Price"), which date is within five business days prior to the filing of this Registration Statement. Represents shares of Common Stock that were automatically added to the shares authorized for issuance under the 2019 Plan on January 1, 2026 pursuant to an "evergreen" provision contained in the 2019 Plan. Pursuant to such provision, on January 1st of each year through (and including) January 1, 2029, the number of shares authorized for issuance under the 2019 Plan will be automatically increased by an amount equal to the lesser of: (a) 5% of the total number of shares of capital stock of the Registrant outstanding on December 31 of the preceding calendar year; or (b) such lesser number of shares of Common Stock as the Registrant's board of directors (the "Board") may designate prior to the applicable January 1st. |
| 2 | Pursuant to Rule 416(a) under the Securities Act, this Registration Statement shall also cover any additional shares of Common Stock of the Registrant that become issuable under the Registrant's 2019 Employee Stock Purchase Plan (the "2019 ESPP") by reason of any stock dividend, stock split, recapitalization or other similar transaction. Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rules 457(c) and 457(h) of the Securities Act. The proposed maximum aggregate offering price per unit and proposed maximum aggregate offering price are calculated on the basis of the Average Price, multiplied by 85% which is the percentage of the price per share applicable to purchases under the 2019 ESPP. Represents shares of Common Stock that were automatically added to the shares authorized for issuance under the 2019 ESPP on January 1, 2026 pursuant to an "evergreen" provision contained in the 2019 ESPP. Pursuant to such provision, on January 1st of each year through (and including) January 1, 2029, the number of shares authorized for issuance under the 2019 ESPP will be automatically increased by an amount equal to the lesser of: (a) 1% of the total number of shares of capital stock outstanding on December 31 of the preceding calendar year; (b) 411,935 shares; or (c) such lesser number of shares of Common Stock as the Board may designate prior to the applicable January 1st. | Pursuant to Rule 416(a) under the Securities Act, this Registration Statement shall also cover any additional shares of Common Stock of the Registrant that become issuable under the Registrant's 2019 Employee Stock Purchase Plan (the "2019 ESPP") by reason of any stock dividend, stock split, recapitalization or other similar transaction. Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rules 457(c) and 457(h) of the Securities Act. The proposed maximum aggregate offering price per unit and proposed maximum aggregate offering price are calculated on the basis of the Average Price, multiplied by 85% which is the percentage of the price per share applicable to purchases under the 2019 ESPP. Represents shares of Common Stock that were automatically added to the shares authorized for issuance under the 2019 ESPP on January 1, 2026 pursuant to an "evergreen" provision contained in the 2019 ESPP. Pursuant to such provision, on January 1st of each year through (and including) January 1, 2029, the number of shares authorized for issuance under the 2019 ESPP will be automatically increased by an amount equal to the lesser of: (a) 1% of the total number of shares of capital stock outstanding on December 31 of the preceding calendar year; (b) 411,935 shares; or (c) such lesser number of shares of Common Stock as the Board may designate prior to the applicable January 1st. | Pursuant to Rule 416(a) under the Securities Act, this Registration Statement shall also cover any additional shares of Common Stock of the Registrant that become issuable under the Registrant's 2019 Employee Stock Purchase Plan (the "2019 ESPP") by reason of any stock dividend, stock split, recapitalization or other similar transaction. Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rules 457(c) and 457(h) of the Securities Act. The proposed maximum aggregate offering price per unit and proposed maximum aggregate offering price are calculated on the basis of the Average Price, multiplied by 85% which is the percentage of the price per share applicable to purchases under the 2019 ESPP. Represents shares of Common Stock that were automatically added to the shares authorized for issuance under the 2019 ESPP on January 1, 2026 pursuant to an "evergreen" provision contained in the 2019 ESPP. Pursuant to such provision, on January 1st of each year through (and including) January 1, 2029, the number of shares authorized for issuance under the 2019 ESPP will be automatically increased by an amount equal to the lesser of: (a) 1% of the total number of shares of capital stock outstanding on December 31 of the preceding calendar year; (b) 411,935 shares; or (c) such lesser number of shares of Common Stock as the Board may designate prior to the applicable January 1st. | Pursuant to Rule 416(a) under the Securities Act, this Registration Statement shall also cover any additional shares of Common Stock of the Registrant that become issuable under the Registrant's 2019 Employee Stock Purchase Plan (the "2019 ESPP") by reason of any stock dividend, stock split, recapitalization or other similar transaction. Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rules 457(c) and 457(h) of the Securities Act. The proposed maximum aggregate offering price per unit and proposed maximum aggregate offering price are calculated on the basis of the Average Price, multiplied by 85% which is the percentage of the price per share applicable to purchases under the 2019 ESPP. Represents shares of Common Stock that were automatically added to the shares authorized for issuance under the 2019 ESPP on January 1, 2026 pursuant to an "evergreen" provision contained in the 2019 ESPP. Pursuant to such provision, on January 1st of each year through (and including) January 1, 2029, the number of shares authorized for issuance under the 2019 ESPP will be automatically increased by an amount equal to the lesser of: (a) 1% of the total number of shares of capital stock outstanding on December 31 of the preceding calendar year; (b) 411,935 shares; or (c) such lesser number of shares of Common Stock as the Board may designate prior to the applicable January 1st. | Pursuant to Rule 416(a) under the Securities Act, this Registration Statement shall also cover any additional shares of Common Stock of the Registrant that become issuable under the Registrant's 2019 Employee Stock Purchase Plan (the "2019 ESPP") by reason of any stock dividend, stock split, recapitalization or other similar transaction. Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rules 457(c) and 457(h) of the Securities Act. The proposed maximum aggregate offering price per unit and proposed maximum aggregate offering price are calculated on the basis of the Average Price, multiplied by 85% which is the percentage of the price per share applicable to purchases under the 2019 ESPP. Represents shares of Common Stock that were automatically added to the shares authorized for issuance under the 2019 ESPP on January 1, 2026 pursuant to an "evergreen" provision contained in the 2019 ESPP. Pursuant to such provision, on January 1st of each year through (and including) January 1, 2029, the number of shares authorized for issuance under the 2019 ESPP will be automatically increased by an amount equal to the lesser of: (a) 1% of the total number of shares of capital stock outstanding on December 31 of the preceding calendar year; (b) 411,935 shares; or (c) such lesser number of shares of Common Stock as the Board may designate prior to the applicable January 1st. | Pursuant to Rule 416(a) under the Securities Act, this Registration Statement shall also cover any additional shares of Common Stock of the Registrant that become issuable under the Registrant's 2019 Employee Stock Purchase Plan (the "2019 ESPP") by reason of any stock dividend, stock split, recapitalization or other similar transaction. Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rules 457(c) and 457(h) of the Securities Act. The proposed maximum aggregate offering price per unit and proposed maximum aggregate offering price are calculated on the basis of the Average Price, multiplied by 85% which is the percentage of the price per share applicable to purchases under the 2019 ESPP. Represents shares of Common Stock that were automatically added to the shares authorized for issuance under the 2019 ESPP on January 1, 2026 pursuant to an "evergreen" provision contained in the 2019 ESPP. Pursuant to such provision, on January 1st of each year through (and including) January 1, 2029, the number of shares authorized for issuance under the 2019 ESPP will be automatically increased by an amount equal to the lesser of: (a) 1% of the total number of shares of capital stock outstanding on December 31 of the preceding calendar year; (b) 411,935 shares; or (c) such lesser number of shares of Common Stock as the Board may designate prior to the applicable January 1st. | Pursuant to Rule 416(a) under the Securities Act, this Registration Statement shall also cover any additional shares of Common Stock of the Registrant that become issuable under the Registrant's 2019 Employee Stock Purchase Plan (the "2019 ESPP") by reason of any stock dividend, stock split, recapitalization or other similar transaction. Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rules 457(c) and 457(h) of the Securities Act. The proposed maximum aggregate offering price per unit and proposed maximum aggregate offering price are calculated on the basis of the Average Price, multiplied by 85% which is the percentage of the price per share applicable to purchases under the 2019 ESPP. Represents shares of Common Stock that were automatically added to the shares authorized for issuance under the 2019 ESPP on January 1, 2026 pursuant to an "evergreen" provision contained in the 2019 ESPP. Pursuant to such provision, on January 1st of each year through (and including) January 1, 2029, the number of shares authorized for issuance under the 2019 ESPP will be automatically increased by an amount equal to the lesser of: (a) 1% of the total number of shares of capital stock outstanding on December 31 of the preceding calendar year; (b) 411,935 shares; or (c) such lesser number of shares of Common Stock as the Board may designate prior to the applicable January 1st. | Pursuant to Rule 416(a) under the Securities Act, this Registration Statement shall also cover any additional shares of Common Stock of the Registrant that become issuable under the Registrant's 2019 Employee Stock Purchase Plan (the "2019 ESPP") by reason of any stock dividend, stock split, recapitalization or other similar transaction. Estimated solely for the purpose of calculating the amount of the registration fee pursuant to Rules 457(c) and 457(h) of the Securities Act. The proposed maximum aggregate offering price per unit and proposed maximum aggregate offering price are calculated on the basis of the Average Price, multiplied by 85% which is the percentage of the price per share applicable to purchases under the 2019 ESPP. Represents shares of Common Stock that were automatically added to the shares authorized for issuance under the 2019 ESPP on January 1, 2026 pursuant to an "evergreen" provision contained in the 2019 ESPP. Pursuant to such provision, on January 1st of each year through (and including) January 1, 2029, the number of shares authorized for issuance under the 2019 ESPP will be automatically increased by an amount equal to the lesser of: (a) 1% of the total number of shares of capital stock outstanding on December 31 of the preceding calendar year; (b) 411,935 shares; or (c) such lesser number of shares of Common Stock as the Board may designate prior to the applicable January 1st. |

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## Exhibit 5.1

**Exhibit 5.1**

![cooleylogo2a.jpg](cooleylogo2a.jpg)

Carlos Ramirez

+1 858 550 6157

cramirez@cooley.com

February 26, 2026

Castle Biosciences, Inc.

1500 W. Parkwood Ave, Suite 400

Friendswood, Texas 77546

Ladies and Gentlemen:

We have acted as counsel to Castle Biosciences, Inc., a Delaware corporation (the "***Company***"), in connection with the filing by the Company of a Registration Statement on Form S-8 (the "***Registration Statement***") with the Securities and Exchange Commission covering the offering of up to 1,781,178 shares (the "***Shares***") of the Company's Common Stock, $0.001 par value per share ("***Common Stock***"), consisting of (i) 1,484,315 shares of Common Stock issuable pursuant to the Company's 2019 Equity Incentive Plan (the "***Incentive Plan***") and (ii) 296,863 shares of Common Stock issuable pursuant to the Company's 2019 Employee Stock Purchase Plan (together with the Incentive Plan, the "***Plans***").

In connection with this opinion, we have examined and relied upon (a) the Registration Statement and the related prospectuses, (b) the Plans, (c) the Company's certificate of incorporation and bylaws, each as currently in effect, and (d) such other records, documents, opinions, certificates, memoranda and instruments as in our judgment are necessary or appropriate to enable us to render the opinion expressed below. We have assumed the genuineness of all signatures, the authenticity of all documents submitted to us as originals, the conformity to originals of all documents submitted to us as copies, the accuracy, completeness and authenticity of certificates of public officials; and the due authorization, execution and delivery of all documents by all persons other than by the Company. As to certain factual matters, we have relied upon a certificate of an officer of the Company and have not independently verified such matters.

Our opinion is expressed only with respect to the General Corporation Law of the State of Delaware. We express no opinion to the extent that any other laws are applicable to the subject matter hereof and express no opinion and provide no assurance as to compliance with any federal or state securities law, rule or regulation.

On the basis of the foregoing, and in reliance thereon, we are of the opinion that the Shares, when sold and issued in accordance with the Plans, the Registration Statement and the related prospectuses, will be validly issued, fully paid and nonassessable (except as to Shares issued pursuant to deferred payment arrangements, which will be fully paid and nonassessable when such deferred payments are made in full).

This opinion is limited to the matters expressly set forth in this letter, and no opinion should be implied, or may be inferred, beyond the matters expressly stated. This opinion speaks only as to law and facts in effect or existing as of the date hereof, and we have no obligation or responsibility to update or supplement this opinion to reflect any facts or circumstances that may hereafter come to our attention or any changes in law that may hereafter occur.

Cooley LLP 10265 Science Center Drive, San Diego, CA 92121

t: (858) 550-6000 f: (858) 550-6420 cooley.com

------

We consent to the filing of this opinion as an exhibit to the Registration Statement. In giving such consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act of 1933, as amended, or the rules and regulations of the Commission thereunder.

Sincerely,

Cooley LLP

By: <u>/s/ Carlos Ramirez</u>&nbsp;&nbsp;&nbsp;&nbsp;

Carlos Ramirez

Cooley LLP 10265 Science Center Drive, San Diego, CA 92121

t: (858) 550-6000 f: (858) 550-6420 cooley.com

## Exhibit 23.1

**Exhibit 23.1**

**Consent of Independent Registered Public Accounting Firm**

We consent to the use of our report dated February 26, 2026, with respect to the consolidated financial statements of Castle Biosciences, Inc. and subsidiaries, and the effectiveness of internal control over financial reporting, incorporated herein by reference.

/s/ KPMG LLP

Houston, Texas

February 26, 2026

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