[Immunohistochemical and genetic profiles of melanomas with spindle cell morphology]

to comparatively study the immunohistochemical profile and to analyze mutations in the BRAF and N-RAS genes.

The spindle cell melanomas taken from the Institute's archives were divided into 6 groups according to the results of clinical and morphological analyses and follow-up studies. Immunohistochemical examination was conducted in 58 cases, including 19 nodular spindle cell melanomas, 10 superficial spreading melanomas, 4 combined melanomas, 8 sarcoma- toid melanomas, 13 mixed desmoplastic melanomas, and 4 pure desmoplastic melanomas.

All tumors of the spectrum in question expressed S100, SOX10, KBA.62, nestin, and cyclin D1. The rate of positive staining was 80% for MITF, 69% for PNL2, 61% for HMB45, 58% for Melan A, 36% for CD117, and 35% for SMA. The expression of HMB45 and Melan A was diffuse and marked in the groups of nodular and superficial spreading melanomas; sarcomatoid and mixed desmoplastic melanomas showed only scattered stained cells; pure desmoplastic melanomas were negative to these markers. SMA immunoexpression was observed in only sarcomatoid and desmoplastic types. Dual S100 staining showed a separate actin-positive myofibroblast-like population disappearing in more cellular zones. EMA, claudin 1, and DOG1 were negative in all cases. BRAFV expression was detected in 14% (in 2 nodular and 1 superficial spreading melanomas) and correlated with the presence of mutation. NRAS mutation was found in 1 nodular spindle cell melanoma. Desmoplastic melanomas did not harbor the above mutations.

This study indicates the variant heterogeneity of spindle cell melanomas, as confirmed by clinical, morphological, immunohistochemical, and molecular examinations. The findings may be useful in the differential diagnosis of these tumors.