Combined high-grade basal cell carcinoma and malignant melanoma of the skin ("malignant basomelanocytic tumor"): report of two cases and review of the literature.

We describe two cases of a malignant cutaneous neoplasm with combined phenotypical features of high-grade basal cell carcinoma and malignant melanoma. Some tumor cells showed a keratinocytic phenotype (cytokeratins, p63) and others a melanocytic phenotype (HMB-45, MART-1, Melan-A, S100-protein). We favor the hypothesis of a tumor with bidirectional keratinocytic and melanocytic differentiation, an exceptionally rare event.