Accuracy of pathologic techniques for the diagnosis of metastatic melanomain sentinel lymph nodes

Background: Sentinel lymph node (SLN) biopsy can accurately predict the pre sence of metastatic melanoma (MM) and has been used to identify patients wi th occult metastases. We present an analysis of the sensitivity and specifi city of standard pathological techniques including intraoperative frozen se ction, permanent section, and immunohistochemistry in diagnosing MM within the SLN. Methods: Sixty-nine consecutive patients with primary malignant melanoma th ickness of >1.0 mm or thinner lesions invading the reticular dermis (Clark level TV) who underwent SLN biopsy were reviewed. Lymph nodes were examined intraoperatively by frozen section (FS), permanent section (H&E), and by i mmunohistochemistry (IH) for S-100 protein and HMB45. Results: MM was found in 14 of 69 cases (20%). Permanent section H&E was pe rformed in all cases, FS in 64 cases, and IH in 65 cases. FS analysis diagn osed MM in 4 of 14 cases (29%), was suspicious in 2 of 14 (14%), and falsel y negative (FN) in 8 of 14 (57%) ultimately found to be positive with furth er workup. Within the FN group, MM was identified on review of the original FS slides in 3 of 8 cases (38%). Furthermore, within the FN group, the rem aining 5 cases were identified as positive for MM by either permanent and/o r deeper H&E sections and IH. IH alone with permanent H&E sections would ha ve diagnosed MM in only 8 of 10 cases (80%) that were FS negative or suspic ious. In no cases was MM identified by IH alone with the permanent and deep er H&E sections being negative. It is noteworthy that no false-positive cas es were identified. Conclusions: Intraoperative FS has low sensitivity in identifying MM within the SLN. IH alone does not increase the diagnostic yield. A combination of permanent H&E sections with deeper levels and S-100 and HMB45 IH dramatica lly increases the overall diagnostic sensitivity of SLN biopsy. Definitive diagnosis should await permanent H&E sections and IH staining.