Primary malignant melanoma with rhabdoid features: a histologic and immunocytochemical study of three cases.

Malignant rhabdoid tumors are morphologically characterized by the presence of sheets of large polygonal cells with abundant cytoplasm containing eosinophilic inclusions. They have vesicular nuclei, often with prominent central nucleoli. The term rhabdoid tumor was originally coined to describe a group of rare, aggressive renal neoplasms of childhood. Since then, similar lesions, so-called extrarenal malignant rhabdoid tumors have been increasingly reported. The evidence to date suggests that, at least in extrarenal locations, rhabdoid tumors do not constitute a homogeneous entity, but rather represent the shared morphological pattern of a diverse range of malignant neoplasms. Although such rhabdoid features are not uncommon in metastatic malignant melanoma, they have only once been briefly described in a primary lesion. We report three further cases of cutaneous primary malignant melanoma with rhabdoid morphology.