Lipomatous mixed tumor of the skin with cystic formation affecting the upper lip: A case report.

Mixed tumor of the skin (MTS) is a rare neoplasm derived from the sweat glands with a reported frequency of 0.01-0.098% among all primary skin tumors. MTS often occurs in the head and neck region and is characterized by a mixture of epithelial, myoepithelial and stromal components. MTS also shows various morphological patterns, thus the presence of variants with rare components and its rarity make the clinical diagnosis even more difficult. A 47-year-old man was referred due to a painless, slowly growing, exophytic swelling intracutaneous mass of the upper lip. Magnetic resonance imaging revealed that the mass was a solid tumor with a fatty component in the proximal portion, while the distal portion was cystic and possibly contained highly viscous fluid. The mass was located between the skin and the orbicularis oris muscle in the upper lip. Excisional biopsy was performed and the lesion showed two intriguing features: A tumor with extensive lipomatous stroma and some large cysts. It was histopathologically diagnosed as lipomatous MTS with cystic formation in the upper lip. No evident signs of recurrence were observed during follow-up. The present report describes this case and includes a brief literature review of reported cases in the lip, since MTS can be confused with various skin lesions in clinical settings due to this rarity. Recognition by clinicians of different variants of MTSs, including the present case, is important for preventing erroneous diagnosis and treatment.