Challenges in sentinel node pathology in the era of adjuvant treatment.

Background With the approval of adjuvant therapy for stage III melanoma, accurate staging is more important than ever. Sentinel node biopsy (SNB) is an accurate staging tool, yet the presence of capsular nevi (CN) can lead to a false-positive diagnosis. Patients and Methods Retrospective analysis of the American Joint Committee on Cancer 7th edition stage IIIA melanoma patients who were treated at our institute between 2000 and 2015. SNB slides were reviewed for this study by an expert melanoma pathologist. Results Of 159 eligible patients, 14 originally diagnosed with metastatic melanoma merely had CN (8.8%). Another two merely had melanophages (1.3%). Thus, 10.1% of SNs were considered false positive after revision. In 12 patients, the SN tumor burden was originally reported as larger than 1 mm but turned out to be less than 1 mm. Four patients originally reported as SN tumor burden less than 1 mm before revision turned out to have larger than 1 mm. These patients might have been over- or undertreated in the current era of adjuvant therapy for stage III melanoma. Conclusions Distinguishing metastatic melanoma from benign CN and melanophages can be a diagnostic challenge. We plead for an expert pathologists' review, especially when using the SNB + results to determine treatment consequences.