Psammomatoid ossifying fibromas:: Immunohistochemical analysis and differential diagnosis with psammomatous meningiomas of craniofacial bones

Objective. To clarify the role of immunohistochemistry in the diagnosis of psammomatoid ossifying fibroma (PSOF conventional cemento-ossifying fibroma (COF), and psammomatous meningioma (PM) of the craniofacial skeleton. Study design. The histology and immunohistochemistry of 4 PSOFs, 6 COFs, and 7 PMs was studied. Antibodies included EMA, cytokeratins, smooth muscle actin (SMA), desmin, vimentin, CD34, CD10, S-100 protein, and glial fibrillary acidic protein (GFAP). Results. All PSOFs showed multiple round ossicles homogeneously distributed within a fibroblastic stroma. Psammomatous meningiomas had meningothelial features. All tumors, except I COF, were positive for EMA. All of them expressed vimentin, and none showed cytokeratins. Staining for SMA and S-100 protein was variable. CD10 was positive in all cases except 2 meningiomas. CD34 and GFAP stained only I case of meningioma each. Conclusions. The diagnosis of PSOF should rest on histologic features. An incorrect diagnosis of meningioma based on the expression of EMA should be avoided.