# EDGAR Filing Document

**Accession Number:** 0001065698
**File Stem:** 0000912938-26-000474
**Filing Date:** 2026-4
**Character Count:** 17675
**Document Hash:** 2c09025197ee5feb1a6ae81f6a46ec26
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0000912938-26-000474.hdr.sgml**: 20260429

**ACCESSION NUMBER**: 0000912938-26-000474

**CONFORMED SUBMISSION TYPE**: 497K

**PUBLIC DOCUMENT COUNT**: 3

**FILED AS OF DATE**: 20260429

**DATE AS OF CHANGE**: 20260429

**EFFECTIVENESS DATE**: 20260429

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** MFS VARIABLE INSURANCE TRUST III
- **CENTRAL INDEX KEY:** 0001065698

**ORGANIZATION NAME:**
- **EIN:** 000000000
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 497K
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 333-59093
- **FILM NUMBER:** 26911079

**BUSINESS ADDRESS:**
- **STREET 1:** 111 HUNTINGTON AVENUE
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02199
- **BUSINESS PHONE:** 617-954-5000

**MAIL ADDRESS:**
- **STREET 1:** 111 HUNTINGTON AVENUE
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02199

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** SUN CAPITAL ADVISERS TRUST
- **DATE OF NAME CHANGE:** 19980709

## Series and Classes Contracts Data

### MFS Mid Cap Value Portfolio (Series ID: S000018843)

| Class ID   | Class Name    | Ticker Symbol   |
|:---|:---|:---|
| C000052149 | Initial Class |  |
| C000052150 | Service Class |  |

![](img_e4a8aec253b84f1.jpg)

SUMMARY PROSPECTUS

*April 30, 2026* 

## MFS <sup>®</sup> Mid Cap Value Portfolio
**Before you invest**, you may want to review the fund's prospectus, which contains more information about the fund and its risks. You can find the fund's prospectus and other information about the fund, including the fund's reports to shareholders and statement of additional information, online at insurancefunds.mfs.com. You can also get this information at no cost by calling 1-800-225-2606 or by sending an e-mail request to orderliterature@mfs.com. The fund's prospectus and statement of additional information, both dated April 30, 2026, as may be amended or supplemented from time to time, are incorporated by reference into this summary prospectus.

---

| | |
|:---|:---|
| &nbsp;&nbsp;**CLASS** | **TICKER SYMBOL** |
| &nbsp;&nbsp;**Initial Class** | N/A |
| &nbsp;&nbsp;**Service Class** | N/A |

---

#### Summary of Key Information

#### Investment Objective
The fund's investment objective is to seek capital appreciation.

#### Fees and Expenses
This table describes the fees and expenses that you may pay when you hold shares of the fund. If the fees and expenses imposed by the insurance company that issued your variable contracts or other eligible investor through which the fund is offered were included, your expenses would be higher.

---

| | | |
|:---|:---|:---|
| **Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):** | **Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):** |  |
|  | **Initial Class** | **Service Class** |
| Management Fee | 0.75% | 0.75% |
| Distribution and/or Service (12b-1) Fees |  | 0.25% |
| Other Expenses | <u>0.05%</u> | <u>0.05%</u> |
| Total Annual Fund Operating Expenses | 0.80% | 1.05% |
| Fee Reductions and/or Expense Reimbursements<sup>1</sup> | <u>(0.01)%</u> | <u>(0.01)%</u> |
| Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements | 0.79% | 1.04% |

---

1 Massachusetts Financial Services Company (MFS) has agreed in writing to waive at least 0.01% of the fund's management fee as part of an agreement pursuant to which MFS has agreed to reduce its management fee by a specified amount if certain MFS mutual fund assets exceed thresholds agreed to by MFS and the fund's Board of Trustees. The agreement to waive at least 0.01% of the management fee will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least April 30, 2027.

VMC-SUM-043026 Page 1 of 4

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MFS Mid Cap Value Portfolio

#### Example
This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. If the fees and expenses imposed by the insurance company that issued your variable contracts or other eligible investor through which an investment in the fund is made were included, your expenses would be higher.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods; your investment has a 5% return each year; and the fund's operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **1 YEAR** | **3 YEARS** | **5 YEARS** | **10 YEARS** |
| **Initial Class Shares** | $81  | $254  | $443  | $989  |
| **Service Class Shares** | $106  | $333  | $578  | $1282  |

---

#### Portfolio Turnover
The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs. These transaction costs, which are not reflected in "Annual Fund Operating Expenses" or in the "Example," affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 24% of the average value of its portfolio.

#### Principal Investment Strategies
MFS (Massachusetts Financial Services Company, the fund's investment adviser) normally invests at least 80% of the fund's net assets in issuers with medium market capitalizations. MFS generally defines medium market capitalization issuers as issuers with market capitalizations similar to those of issuers included in the Russell Midcap<sup>®</sup> Value Index over the last 13 months at the time of purchase. As of March 31, 2026, the range of the market capitalizations of the issuers in the Russell Midcap<sup>®</sup> Value Index was between approximately $907.1 million and $116.8 billion.

#### Effective June 10, 2026, the paragraph directly above is restated in its entirety with the following three paragraphs:
MFS (Massachusetts Financial Services Company, the fund's investment adviser) normally invests at least 80% of the fund's net assets in value companies with medium market capitalizations.

MFS defines medium market capitalization companies as issuers that (i) have market capitalizations within the capitalization range of the Russell Midcap<sup>®</sup> Index over the past 12 months based on the current composition of the index and/or are (ii) classified as a medium capitalization company by an independent third party financial data provider. The market capitalization range of companies considered to have medium capitalizations based on the above criteria will change over time depending on market conditions. For illustrative purposes, March 31, 2026, the range of the market capitalizations of the issuers in the Russell Midcap<sup>®</sup> Index was between approximately $907.1 million and $116.8 billion, and the fund's average weighted market capitalization as of that date was $26.6 billion.

Value companies are companies that MFS believes are undervalued compared to their perceived worth in the marketplace. MFS considers a number of factors when determining whether a company is undervalued, including whether (i) the issuer is included in an index which is representative of value companies; (ii) the issuer is classified as a value company by an independent third party financial data provider and/or (iii) the issuer exhibits the characteristics of a value company, considering metrics such as such as price-to-book ratio, price-to-earnings ratio, and dividend yield relative to the applicable equity market and/or sector of the applicable equity market. Value companies tend to have stock prices that are low relative to their earnings, dividends, assets, or other financial measures.

MFS normally invests the fund's assets primarily in equity securities. Equity securities include common stocks, depositary receipts, equity interests in real estate investment trusts (REITs), and other securities that represent an ownership interest (or right to acquire an ownership interest) in a company or other issuer.

#### Effective June 10, 2026, the following sentence is deleted in its entirety:
MFS focuses on investing the fund's assets in the stocks of companies it believes are undervalued compared to their perceived worth (value companies).

MFS may invest the fund's assets in foreign securities.

MFS normally invests the fund's assets across different industries and sectors, but MFS may invest a significant percentage of the fund's assets in issuers in a single industry or sector.

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual issuers. Quantitative screening tools that systematically evaluate issuers may also be considered.

For purposes of the fund's 80% policy, net assets include the amount of any borrowings for investment purposes.

#### Principal Risks
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

**Investment Selection Risk:** MFS' investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests. In addition, to the extent MFS considers quantitative tools in managing the fund, such tools may not produce the intended results.

**Equity Market Risk/Company Risk:** Equity markets are volatile and can decline significantly in response to changes in, or investor perceptions of, issuer, market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. These conditions can affect a single issuer or type of security, issuers within a broad market sector, industry or geographic region, or the equity markets in general. Certain events can have a dramatic adverse effect on equity markets and may lead to periods of high volatility in an equity market or a segment of an equity market. The value of an investment held by the fund may decline due to factors directly related to the issuer.

**Value Company Risk:** The stocks of value companies can continue to be undervalued for long periods of time and not realize

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MFS Mid Cap Value Portfolio

their expected value and can be more volatile than the market in general.

**Mid Cap Risk:** The stocks of mid cap companies can be more volatile and their shares can be less liquid than those of larger companies.

**Foreign Risk: Exposure to foreign markets through issuers or currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. These factors can make foreign investments, especially those tied economically to countries with developing economies or countries subject to sanctions or the threat of new or modified sanctions, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to these conditions than the U.S. market.**

**REITs Risk:** The risks of investing in REITs include certain risks associated with the direct ownership of real estate and the real estate industry in general. These include risks related to general, regional and local economic conditions; difficulties in valuing and disposing of real estate; fluctuations in interest rates and property tax rates; shifts in zoning laws, environmental regulations and other governmental action; cash flow dependency; increased operating expenses; lack of availability of mortgage funds; losses due to natural disasters; overbuilding; losses due to casualty or condemnation; changes in property values and rental rates; the management skill and creditworthiness of the REIT manager; and other factors. The securities of smaller real estate-related issuers can be more volatile and less liquid than securities of larger issuers and their issuers can have more limited financial resources.

**Focus Risk:** Issuers in a single industry, sector, country, or region can react similarly to market, currency, political, economic, regulatory, geopolitical, environmental, public health, and other conditions, and the fund's performance will be affected by the conditions in the industries, sectors, countries, and regions to which the fund is exposed. Furthermore, investments in particular industries, sectors, countries, or regions may be more volatile than the broader market as a whole.

**Liquidity Risk:** It may be difficult to value, and it may not be possible to sell, certain investments, types of investments, and/or investments in certain segments of the market, and the fund may have to sell certain of these investments at prices or times that are not advantageous in order to meet redemptions or other cash needs.

**Large Shareholder Risk:** From time to time, shareholders of the fund (which may include institutional investors, financial intermediaries, or other MFS funds) may make relatively large redemptions or purchases of fund shares. These transactions may cause the fund to sell securities or invest additional cash, as the case may be, at disadvantageous prices. Redemptions of a large number of shares also may increase transaction and other costs or have adverse tax consequences for shareholders of the fund by requiring a sale of portfolio securities. Purchases of a large number of shares may adversely affect the fund's performance to the extent that it takes time to invest new cash and the fund maintains a larger cash position than it ordinarily would.

#### Performance Information
The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of (i) a broad measure of market performance and (ii) the performance of an additional index that the adviser believes more closely reflects the market segments in which the fund invests.

The fund's past performance does not necessarily indicate how the fund will perform in the future. Updated performance is available at **mfs.com** or by calling 1-877-411-3325. If the fees and expenses imposed by the insurance company that issued your variable contracts or other eligible investor through which an investment in the fund is made were included, they would reduce the returns shown.

#### Initial Class Bar Chart.
![PerformanceBarChartData(2016:15.98, 2017:13.67, 2018:-11.45, 2019:31.12, 2020:3.87, 2021:30.99, 2022:-8.79, 2023:12.73, 2024:13.75, 2025:5.98)](img_92af2728b32d4f1.jpg)

The total return for the three-month period ended March 31, 2026, was 1.09%. During the period(s) shown in the bar chart, the highest quarterly return was 19.90% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (31.01)% (for the calendar quarter ended March 31, 2020).

#### Performance Table.

---

| |
|:---|
| **Average Annual Total Returns** |
| (For the Periods Ended December 31, 2025) |

---

---

| | | | |
|:---|:---|:---|:---|
|  | **1 YEAR** | **5 YEARS** | **10 YEARS** |
| **Initial Class Shares** | 5.98%  | 10.18%  | 9.95%  |
| **Service Class Shares** | 5.75%  | 9.90%  | 9.69%  |
| **Index Comparisons (Reflects no deduction for fees, expenses, or taxes)** |  |  |  |
| Russell 3000<sup>®</sup> Index | 17.15%  | 13.15%  | 14.29%  |
| Russell Midcap<sup>®</sup> Value Index | 11.05%  | 9.83%  | 9.78%  |

---

#### Investment Adviser
MFS serves as the investment adviser for the fund.

#### Portfolio Manager(s)

---

| | | |
|:---|:---|:---|
| **Portfolio Manager** | &nbsp;&nbsp;&nbsp;**Since** | &nbsp;&nbsp;&nbsp;**Title** |
| &nbsp;&nbsp;Richard Offen | &nbsp;&nbsp;&nbsp;2021 | &nbsp;&nbsp;&nbsp;Investment Officer of MFS |
| &nbsp;&nbsp;Kevin Schmitz | &nbsp;&nbsp;&nbsp;2012 | &nbsp;&nbsp;&nbsp;Investment Officer of MFS |
| &nbsp;&nbsp;Brooks Taylor | &nbsp;&nbsp;&nbsp;2012 | &nbsp;&nbsp;&nbsp;Investment Officer of MFS |

---

#### Purchase and Sale of Fund Shares
You should consult with the insurance company that issued your variable contract, or other eligible investor through which your investment in the fund is made, for minimum investment requirements and redemption procedures.

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MFS Mid Cap Value Portfolio

#### Taxes
You should consult with the insurance company that issued your variable contract, or other eligible investor through which your investment in the fund is made, to understand the tax treatment of your investment.

#### Payments to Financial Intermediaries
The fund, MFS, and/or its affiliates may make payments to insurance companies, other financial intermediaries, and all of their affiliates, for distribution and/or other services. These payments may create a conflict of interest for the insurance company or other financial intermediary to include the fund as an investment option in its product or to recommend the fund over another investment option. Ask your financial intermediary or insurance company, or visit your financial intermediary's or insurance company's website, for more information.

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