Dermatofibrosarcoma protuberans (DFSP) is an uncommon intermediate-grade soft tissue sarcoma. The tumor is found preferentially on the trunk, whereas the head and neck region are affected in only 10% to 15% of cases. We report the case of a 44-year-old woman with a 5-month history of an asymptomatic, firm, yellow nodule in the mucosa of the right cheek measuring 2.5 cm. The clinical diagnosis was lipoma and an excisional biopsy was obtained. Histopathological analysis revealed a proliferation of spindle-shaped mesenchymal cells arranged in interlacing fascicles amidst fibrous stroma. Low mitotic activity (2 mitoses per field) and deep cell infiltration into adipose tissue were observed. These features led to the histopathological diagnosis of a malignant low-grade mesenchymal cell tumor. Immunohistochemical analysis revealed negative staining for α-SMA, S-100, and Bcl-2, but positive staining for Ki-67 (18%) and strong and diffuse staining for CD34. These findings were compatible with the diagnosis of DFSP. Only two cases of DFSP in the oral cavity, both involving the cheek mucosa, have been described so far, highlighting the rarity of the present case.
