Sinonasal hemangiopericytomas: a clinicopathologic and immunohistochemical study of seven cases

Sinonasal hemangiopericytoma (SNHPC) is a rare lesion usually of low-grade malignant potential. Aggressive and metastatic cases are uncommon, and experience using adjuvant therapy on these cases has been limited. Tumor-induced osteomalacia has a very rare association with SNHPC. Further, the diagnosis of SNHPC remains one of histologic-pattern recognition. Traditionally, immunohistochemistry has aided in excluding other diagnoses; only vimentin has been consistently expressed by the tumor spindle cells of HPC. Recent studies have shown that Factor XIIIa is also expressed by HPC, (as well as tumors of fibrohistiocytic differentiation) and hence may be yet another helpful positive marker in establishing an immunohistochemical profile.

We identified 7 patients at this institution with SNHPC from 1990 to 1994. Immunohistochemistry was performed on seven formalin-fixed paraffin-embedded tumors utilizing antibodies to factor XIIIa as well as antibodies to vimentin, factor VIII, muscle-specific antigen, cytokeratin, and S-100.

All 7 patients were initially seen with nasal obstruction or epistaxis and underwent surgical resection. The period of follow-up was from 3 months to 14 years (mean 54 months) for 7 patients. Three patients had recurrent disease after 3, 5, and 10 years. The first 2 were known to have been originally treated by polypectomy. One patient required adjuvant radiotherapy for metastatic disease and local extension. One patient was initially seen with tumor-induced osteomalacia which dramatically improved following resection of the lesion. The immunohistochemical profile revealed strong expression of vimentin in 7/7 cases, and of factor XIIIa in 4/7 cases; tumor cells did not express the other markers studied.

Adequate surgical resection with negative margins appears to be the appropriate therapy for SNHPC. Our 1 case associated with tumor-induced osteomalacia was reversible after surgical excision of the tumor. The immunohistochemical results suggest that the pattern of vimentin and factor XIIIa positivity, as well as lack of expression of other markers, is consistent with the diagnosis of HPC, which still remains in the domain of histopathology.