Solitary fibrous tumour of the oral cavity: clinicopathological and immunohistochemical characterization of three cases

Solitary fibrous tumour (SFT) is an uncommon mesenchymal neoplasm rarely lo cated in the oral cavity. To characterize further oral SFT, we describe thr ee new cases. Each tumour originated in the buccal mucosa of a middle-aged/ elderly patient. Histological examination showed well-circumscribed tumours with densely cellular areas alternating with hypocellular areas in a varie dly collagenous, vascular stroma. Mast cells were abundant. The spindle-sha ped, neoplastic cells immunostained strongly for CD34 antigen and vimentin and weakly for bcl-2, but not for epithelial cell markers, a-smooth muscle actin, or neurofilament or S-100 proteins. Compatible with the virtual abse nce of mitoses and of marked nuclear atypia, the overall frequency of proli ferating cells expressing Ki-67 was low. The expression of CD34 was useful in the differential diagnosis. The consistent location in the cheek and exp ansion of one tumour after local trauma does not preclude a traumatic eleme nt in the development of oral SFT.