Extrapleural Solitary fibrous tumor of the oral cavity: proliferation markers, tumor suppressor gene expression, and ultrastructural features

Abstract

Background Extrapleural solitary fibrous tumors (ESFT) were previously classified as hemangiopericytomas (HPCs). With the current WHO classification, HPCs have been incorporated within ESFTs. A myopericytic category includes tumors with pericytic differentiation. Objective Proliferation markers, tumor suppressor gene expression, and ultrastructural features were evaluated with cellular oral ESFTs. Case reports Two females (53 and 52 years old) presented with recurrent oral masses (1 cm and 1.8 cm) involving the anterior facial gingiva and buccal mucosa. Pathology These cellular tumors were composed of a bland plump spindle cell proliferation embedded in a vascular background. The cells were arranged in a storiform pattern. The adjacent soft tissues were infiltrated by tumor with extension to the margins. Tumor cells were diffusely positive for CD34, Bcl-2 and MCM-7, moderately to focally positive for CD99, mildly positive for Mib-1, and focally positive for p53. Smooth muscle actin, muscle-specific actin, and S100 protein were negative. Electron microscopy revealed bland spindle cells with occasional areas of extracellular collagen precipitation. Glycocalyx material coated the cell surfaces. Attachment plaques and smooth muscle differentiation were lacking. Dermatofibrosarcoma protuberans [t(17;22), COL1A1-PDGFB] and pericytic tumor [t(7;12), GLI-ACTB] translocations were not detected by RT-PCR. Conclusion With these cellular oral ESFTs, proliferation markers (Bcl-2, MCM-7) were expressed diffusely in a high proportion of cells, and p53 also was identified focally. Morphology alone does not predict which ESFTs have aggressive or metastatic potential. Complete excision of ESFTs with close clinical follow-up is the recommended treatment.