A case of double cancer involving oral malignant melanoma and gastrointestinal stromal tumor (GIST).

We report a very rare case of double cancer involving palatal malignant melanoma and gastrointestinal stromal tumor (GIST), a rare tumor of the gastrointestinal tract originating from a primitive mesenchymal cell. After chemotherapy, radiation therapy, and treatment with interferon and OK-432, the GIST was resected and the melanoma disappeared. The patient has had no evidence of recurrent tumor, and the patient's clinical course has been uneventful for 1 year. This is probably the first report of synchronous double cancer involving oral malignant melanoma and GIST.