Evaluation of micrometastases in sentinel lymph nodes of cutaneous melanoma: higher diagnostic accuracy with Melan-A and MART-1 compared with S-100 protein and HMB-45.

Accurate diagnosis of micrometastases in sentinel lymph nodes of cutaneous melanoma is critical for proper clinical management. S-100 protein and HMB-45 are the traditional immunomarkers widely used for this purpose. However, the interpretation of micrometastases by these markers is difficult with significant reduction in the diagnostic accuracy. S-100 protein demonstrates immunoreactivity for other nonmelanoma cells and obscures nuclear details, which are crucial for the interpretation of single cell metastases. We compared the new melanoma markers, Melan-A (clone A103) and MART-1 (clone M2-7C10), with S-100 protein and HMB-45, by examining 77 formalin-fixed paraffin-embedded sections of sentinel lymph nodes from 13 cases of primary cutaneous melanoma. CD68 (PG-M1) and hematoxylin-eosin-stained sections were also studied. Four pathologists interpreted the staining pattern after concealing the identity of each immunomarker. Az values (area under receiver operating characteristic curve) with receiver operating characteristic curve were higher with Melan-A (0.9742) and MART-1 (0.9779) compared with S-100 protein (0.8034) and HMB-45 (0.8651), demonstrating a higher diagnostic accuracy with Melan-A and MART-1 with superior detection of melanoma micrometastases. Melan-A and MART-1 showed sharp cytoplasmic immunoreactivity, almost exclusively restricted to the melanoma cells. Therefore, Melan-A and MART-1 are recommended for the evaluation of micrometastases in sentinel lymph nodes of cutaneous melanoma as a routine alternative to S-100 protein and HMB-45.