A rare case of fatal primary cutaneous mucinous carcinoma of the scalp with multiple in-transit and pulmonary metastases

BACKGROUND: Primary cutaneous mucinous carcinoma is a rare neoplasm derived from the sweat glands. It is usually located in the head and neck region, with the eyelids being the most common site of presentation. Recurrence following primary excision is common but metastasis is rare. CASE REPORT: We report a patient presenting with rapidly progressive cutaneous mucinous carcinoma on the right parietal scalp. Systemic work-up failed to reveal an occult primary source. The tumor was treated with Mohs micrographic surgery with clear margins. However, within two months, the patient developed new lesions on the scalp both adjacent to and separate from the original previously excised area, as well as metastasis to the right parotid gland. The patient received adjuvant radiation therapy both to the scalp lesions and to the parotid gland with apparent control of locoregional disease. However, two weeks after completing radiation therapy, the patient was found to have developed pulmonary metastases and died soon thereafter. CONCLUSION: Primary mucinous carcinoma arising in the skin is rare and usually follows an indolent course. We report the rare occurrence of a mucinous carcinoma of the scalp that developed multiple cutaneous tumors caused by in-transit metastases, as well as parotid gland metastases and eventual fatal pulmonary metastases.