Basal cell carcinoma and malignant melanoma cutaneous collision tumor.

Malignant tumors composed of both epithelial and melanocytic populations are exceedingly rare. Because the etiology of these malignant tumors is not yet defined, several authors have argued for the continued cataloging of these lesions. We present a 67-year-old man with a suspicious-appearing lesion on the right forearm; initial biopsy was consistent with a pigmented basal cell carcinoma. On re-excision, a collision of malignant melanoma and basal cell was identified.