Spindle cell lipoma of the oral cavity.

Spindle cell lipoma is typically seen in the neck/trunk region of middle-aged and older men. Rare cases of oral spindle cell lipoma have been reported. An entity described as myxoid lipoma of the oral cavity has rarely been reported but appears to be more properly classified as spindle cell lipoma. We describe the largest series yet of oral spindle cell lipoma involving the tongue (4), buccal mucosa (1), floor of mouth (1), and lip (1). The patients (3M; 4F) ranged from 31 to 88 years old. All presented with mass lesions. All were circumscribed and composed of mature adipocytes admixed with bland spindled cells. In two cases the adipocytes appeared atrophic, imparting a pseudo-lipoblastic appearance. No true lipoblasts were seen and none had the characteristic vasculature of a myxoid liposarcoma or the characteristic hyperchromatic cells of well-differentiated liposarcoma. The stromal background of all cases contained characteristic wiry collagen and myxoid ground substance. The myxoid ground substance was prominent in four cases. Immunohistochemical stains for CD34 highlighted the bland spindle cells in all cases. The combination of the histologic features and the immunoreactivity for CD34 confirmed the diagnosis. Spindle cell lipoma should be considered in the differential diagnosis of oral cavity mesenchymal tumors.