Does needle biopsy cause an increased risk of extracapsular extension in the diagnosis of metastatic lymph node in melanoma?

Background Needle biopsy is a rapid, reliable, and reproducible procedure for histological confirmation of metastatic melanoma localization. Nonetheless, this procedure presents a theoretical risk of a mechanical weakening of the lymph node capsule with perinodal tumor seeding. The objective of the study was to evaluate the incidence of extracapsular extension after needle biopsy in comparison with surgical adenectomy in patients suspected of metastatic lymph node of melanoma. Methods We conducted a retrospective study of 1056 patients who underwent lymphadenectomy for melanoma between 2000 and 2016 in our unit. Sixty‐nine patients were clinically and/or radiologically suspected of metastatic lymph node of melanoma. Patients were divided according to external lymph node biopsy or surgical adenectomy before lymphadenectomy. The primary endpoint was the histopathological identification of extracapsular extension in analyzed lymph nodes. Results The two populations were comparable except for the mitotic index, which was more frequently > 1/mm2 in the group with surgical adenectomy (P = 0.005). The proportion of extracapsular extension was significantly greater in the needle biopsy group (28/37) than in patients who underwent surgical adenectomy (14/32) (P = 0.0067; OR = 4 [95% CI: 1.4–11]). Conclusion Our results suggest an increased risk of extracapsular extension after external lymph node biopsy in cases of suspicion of metastatic lymph node of melanoma. Thus, this encourages us to prefer surgical adenectomy in patients with suspected adenopathy accessible surgically. In other cases, needle biopsy should be carried out under radiological guidance using devices limiting tumor seeding.