Assessment of the Diagnostic Accuracy of Core Needle Biopsies in the Diagnosis of Lymphoma
Authors: Ye Xiangyun , Tucker Catherine , Gardner Christopher , Redilla Austin , Uppal Guldeep , Binder Adam F. 
Published: November 2020

Background: Excisional biopsy of the involved lymph node or tissue is the gold standard for diagnosing lymphoma. However, excisional biopsies are not always feasible depending on the location of the tumor. Recent literature suggests that novel diagnostic techniques such as immunohistochemistry, flow cytometry, FISH/Cytogenetics enhance the accuracy of less-invasive diagnostic procedures like Core needle biopsy (CNB) such that they are comparable to that of excisional biopsies. However, these studies were small and need further confirmation. Despite this, at our institution, CNB has been ordered with increasing frequency even for lymph nodes that can be surgically excised with ease (from 2016-2018 CNB for diagnosis of lymphoma increased from 19% to 31.6% of all lymph node biopsies for suspected lymphoma, with a slight decrease to 27.7% in 2019). Herein we review the diagnostic odds ratio and adequacy of a large dataset of patients who underwent either excisional or CNB at our institution.
Methods: We performed a retrospective cohort study based on the results of lymph node biopsies collected from patients between January 1, 2016, and December 31, 2019, at Thomas Jefferson University Hospital. Biopsies performed externally and referred to our institution for analysis were excluded. The diagnostic odds ratio and confidence intervals were calculated using the Baptista-Pike method. The specimens were considered diagnostically inadequate if: 1. There was not enough lesional tissue for diagnosis or 2. Lesional tissue was present but the disease process was unable to be fully characterized. Adequacy of the specimens were then compared for statistical significance using a chi-squared test. Additional data collected included details of the biopsy procedure including whether a fine needle aspirate was collected, and pathologic workup such as ancillary studies (i.e. flow cytometry, cytogenetics, fluorescence in situ hybridization (FISH)), and reviewing pathologist.
Results: A total of 579 biopsies were collected for review, 122 of which were excluded due to failure to meet our inclusion criteria. Thus, 457 biopsy samples were included in the final analysis, consisting of 339 excisional biopsy samples and 118 CNB samples. Excisional biopsies had adequate tissue to make a diagnosis 96.8% (328) of the time, while CNB's had adequate tissue to make a diagnosis 56.8% (67) of the time. The diagnostic odds ratio of CNB was determined to be 0.03583, [95% confidence interval {CI}: 0.01695 to 0.07532] (Baptista-Pike), p &lt;0.0001 (Chi square). The 3 most common sites for a CNB were axillary (34.7%), Inguinal (14.4%), and supraclavicular (11.9%). For more details regarding lymphoma subtype, biopsy location, and reviewing pathologist see table 1. Inadequate core needle biopsy samples occurred regardless of needle size (12 gauge 0/4, 14 gauge 4/22, 16 gauge 0/2, 18 gauge 27/56, 20 gauge 5/13, 22 gauge 1/1, 25 gauge 0/1) and did not show statistically significant correlation (p = 0.0591, Chi square). Nineteen CNB's did not have needle gauge size available for analysis.
Conclusions: Despite a recent trend moving away from excisional biopsies at our institution, our results indicate that excisional biopsy of lymph nodes in patients with suspected lymphoma should remain the standard of care. Interestingly the 3 most common sites in which a CNB was performed are easily accessible for excisional lymph node biopsy. Further research is needed to understand the reason for the trend away from excisional biopsy at our institution. Based on this preliminary research a quality improvement initiative is being implemented to reduce the number of core needle biopsies for suspected lymphoma, particularly for sites in which the lymph node can be easily excised.

Disclosures
Binder: Sanofi: Consultancy; Janssen: Membership on an entity's Board of Directors or advisory committees.