MALIGNANT-MELANOMA SHOWING SMOOTH-MUSCLE DIFFERENTIATION

A unique ease of a metastatic non-desmoplastic sarcomatoid malignant m elanoma in an axillary lymph node showing smooth muscle differentiatio n in a 54 year old woman is described. The tumour cells exhibited alph a-smooth muscle actin, HHF-35 and desmin positivity but were negative for S100 protein and HMB-45. Ultrastructural examination revealed smoo th muscle phenotype and there was no evidence of myofibroblastic diffe rentiation, a feature described previously in desmoplastic melanomas.