Sinonasal-type hemangiopericytoma of the nasal cavity and paranasal sinus.

Sinonasal-type hemangiopericytoma is a very rare disease. A 64-year-old man was admitted to our hospital because of nasal obstruction. Nasal endoscopy showed a polyp in the right nasal cavity. Imaging modalities including CT and MRI revealed polypoid tumors in the right nasal cavity and right sphenoid sinus. Excision of the tumors was performed. Macroscopically, the nasal tumor was reddish and focally cystic, and the tumor of the sphenoid sinus was reddish and solid. Microscopically, round and polygonal cells were seen to proliferate monotonously in a medullary fashion. Each tumor cell had a vesicular nucleus and amphophilic cytoplasm. The cellularity was high and mitotic figures were recognized in 6 per 10 high-power fields. Many thin-walled vessels were embedded within the tumor. No collagenization was recognized. A silver stain showed that fine argyrophilic fibers encased individual cells and a few cell nests. Mild invasion into the surrounding tissue was recognized in focal areas. The tumor showed focal cystic and hemorrhagic changes. Immunohistochemically, the tumor cells were positive for vimentin, bcl-2 and factor XIIIa, and negative for cytokeratins, epithelial membrane antigen, CD34, desmin, α-smooth muscle antigen, myoglobin, myogenin, CD31, KIT, p53 protein, CD99, and factor VIII-related antigen. Ki-67 labeling was 17%. The pathological diagnosis was low-grade malignant sinonasal-type hemangiopericytoma. The patient was followed up, but no recurrence has been seen 4 years after the operation.