Sinonasal undifferentiated carcinoma metastatic to the skin.

Sinonasal undifferentiated carcinoma (SNUC) is an aggressive malignancy of disputed histogenesis that arises in the sinonasal tract and has an extremely poor prognosis. Despite multimodality treatment with surgical resection, radiation, and chemotherapy, recurrence is common. The tumor spreads by direct local extension, but also metastasizes to lymph nodes, brain, lung and bone. To date, reports of metastasis to the skin have not been published. We report a case of a 58-year-old woman diagnosed with SNUC who underwent surgical resection of the tumor followed by chemoradiation. The tumor soon recurred, and she required wide re-excision. Two months after this procedure, she developed multiple dermal nodules in the head and neck region, clinically suspicious for metastases. Biopsy of a nodule from the right neck revealed a poorly differentiated carcinoma, with morphological and immunohistochemical findings consistent with a metastasis of the patient's known SNUC. We conclude that the skin may be a rare site of metastasis of SNUC, and in some cases may be the presenting sign of tumor recurrence despite aggressive multimodality treatment.