Simultaneous malignant melanoma and squamous cell carcinoma of the oral cavity: a case report.

Primary malignant melanoma of the oral cavity is rare. The incidence of oral melanoma constitutes between 0.2% and 8.0% of all melanomas, although higher percentages are reported in Japanese and other nonwhite races. In contrast, squamous cell carcinoma is the most common malignant neoplasm in the oral region. Multiple cancers may develop independently over the course of time in one organ, or double cancers may develop separately in different organs. Both types of cancer are collectively referred to as multiple primary cancers. The simultaneous occurrence of two histologically distinct primary malignancies in the same organ is extremely rare. We present a case of simultaneous malignant melanoma in association with squamous cell carcinoma of the oral cavity.