Delayed Diagnosis of Primary Sinonasal Mucosal Melanoma.

Primary sinonasal mucosal melanoma (SNMM) is a rare and highly aggressive malignancy that is frequently diagnosed at advanced stages because of its nonspecific presentation. We report the case of a 70-year-old Peruvian woman who presented with a six-month history of recurrent unilateral epistaxis refractory to direct compression, chemical cauterization, and nasal packing, associated with progressive nasal obstruction, facial pain, foul-smelling nasal discharge, and significant weight loss. Nasofibrolaryngoscopy revealed a friable pigmented mass arising from the left nasal cavity. Computed tomography demonstrated a lesion originating from the inferior turbinate without evidence of adjacent bone invasion. Histopathological examination showed an epithelioid malignant neoplasm with moderate pigmentation and a high mitotic index (11 mitoses/mm²), and immunohistochemistry was positive for SOX10, confirming the diagnosis of primary SNMM. This case highlights the diagnostic challenge of SNMM and emphasizes that persistent unilateral epistaxis refractory to conventional treatment should prompt early endoscopic evaluation to exclude structural lesions, including uncommon sinonasal malignancies.