Collagenous spherulosis in a schwannoma.

"Collagenous spherulosis" is the term used to describe striking concentric and radiating formations of collagen in tumors. It was originally used for these formations in epithelial tumors of the breast and subsequently in tumors of salivary glands. Recently, the histologic, immunohistochemical, and ultrastructural features were described in a chondroid syringoma. We report a case of collagenous spherulosis in a schwannoma. Routine histologic sections showed a circumscribed tumor in which the predominant feature was radiating fibrillar structures that tended to compress the cellular component of the tumor. Immunohistochemical studies showed that the cells were positive for glial fibrillary acidic protein (GFAP) and S-100 protein but negative for keratin. EMA showed a positive reaction in a thin band of cells around the periphery of the tumor consistent with perineurial cells. Type IV collagen stained around the periphery of the collagen formations. Electron microscopy revealed that the material was consistent with collagen. Our findings were essentially identical to those reported in the chondroid syringoma. This case confirms the findings of the previous study and shows that these unusual formations are not confined to tumors of epithelial origin. Because the architecture of the tumor is distorted, special stains may be required for correct diagnosis.