Sinonasal tract and nasopharyngeal melanomas: a clinicopathologic study of 115 cases with a proposed staging system.

Primary sinonasal tract mucosal malignant melanomas are uncommon tumors that are frequently misclassified, resulting in inappropriate clinical management. A total of 115 cases of sinonasal tract mucosal malignant melanoma included 59 females and 56 males, 13-93 years of age (mean 64.3 years). Patients presented most frequently with epistaxis (n = 52), mass (n = 42), and/or nasal obstruction (n = 34) present for a mean of 8.2 months. The majority of tumors involved the nasal cavity (n = 34), septum alone, or a combination of the nasal cavity and sinuses (n = 39) with a mean size of 2.4 cm. Histologically, the tumors were composed of a variety of cell types (epithelioid, spindled, undifferentiated), frequently arranged in a peritheliomatous distribution (n = 39). Immunohistochemical studies confirmed the diagnosis of sinonasal tract mucosal malignant melanomas with positive reactions for S-100 protein, tyrosinase, HMB-45, melan A, and microphthalmia transcription factor. Sinonasal tract mucosal malignant melanomas need to be considered in the differential diagnosis of most sinonasal malignancies, particularly carcinoma, lymphoma, sarcoma, and olfactory neuroblastoma. Surgery accompanied by radiation and/or chemotherapy was generally used. The majority of patients developed a recurrence (n = 79), with 75 patients dying with disseminated disease (mean 2.3 years), whereas 40 patients are either alive or had died of unrelated causes (mean 13.9 years). A TNM-type classification separated by anatomic site of involvement and metastatic disease is proposed to predict biologic behavior.