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 immuno-markers 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 demonstrate s immunoreactivity for other nonmelanoma cells and obscures nuclear details , which are crucial for the interpretation of single cell metastases. We co mpared 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 paraff in-embedded sections of sentinel lymph nodes from 13 cases of primary cutan eous melanoma. CD68 (PG-MI) and hematoxylin-eosin-stained sections were als o studied. Four pathologists interpreted the staining pattern after conceal ing the identity of each immunomarker. Az values (area under receiver opera ting characteristic curve) with receiver operating characteristic curve wer e higher with Melan-A (0.9742) and MART-1 (0.9779) compared with S-100 prot ein (0.8034) and HMB-45 (0.8651), demonstrating a higher diagnostic accurac y with Melan-A and MART-1 with superior detection of melanoma micrometastas es. Melan-A and MART-1 showed sharp cytoplasmic immunoreactivity, almost ex clusively restricted to the melanoma cells. Therefore, Melan-A and MART-1 a re recommended for the evaluation of micrometastases. in sentinel lymph nod es of cutaneous melanoma as a routine alternative to S-100 protein and HMB- 45.