Here we describe a clinically amelanotic malignant melanoma in the maxilla of a 49-year-old man. The tumor appeared as a slightly reddish mass without pigmentation. Examination of a biopsy specimen showed the tumor to be composed of a solid proliferation of round and spindle cells with atypia. Although not obvious in H-E-stained sections, melanin pigment was seen after Fontana-Masson staining in only a few tumor cells. Many tumor cells showed positive immunoreactivity for S-100 protein, NSE and antimelanoma antibody, HMB-45.
Radiotherapy and chemotherapy were performed, and the primary and neck metastatic tumors regressed. However, the patient died of multiple distant metastases. Postmortem examination revealed darkly brown-stained peritoneal metastasis, but no pigmentation at other metastatic sites.