Collision of primary malignant neoplasms on the skin: the connection between malignant melanoma and basal cell carcinoma.

Several studies have reported the association of cutaneous malignant melanomas (MM) with carcinomas. Collision malignancies cases from our files were retrieved. Among a series of 78,000 primary cutaneous cancers, 11 were collision tumors of MM with basal cell carcinoma and 106 were basosquamous carcinomas while no association was found between MM and squamous cell carcinomas. It is concluded that coexisting and confluent malignancies of the skin might not always be a random event.