SINONASAL HEMANGIOPERICYTOMAS - A CLINICOPATHOLOGICAL AND IMMUNOHISTOCHEMICAL STUDY OF 7 CASES

Background. Sinonasal hemangiopericytoma (SNHPC) is a rare lesion usua lly 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 express ed by the tumor spindle cells of HPC. Recent studies have shown that F actor XIIIa is also expressed by HPC, (as well as tumors of fibrohisti ocytic differentiation) and hence may be yet another helpful positive marker in establishing an immunohistochemical profile. Methods. We ide ntified 7 patients at this institution with SNHPC from 1990 to 1994. I mmunohistochemistry was performed on seven formalin-fixed paraffin-emb edded tumors utilizing antibodies to factor XIIIa as well as antibodie s to vimentin, factor VIII, muscle-specific antigen, cytokeratin, and S-100. Results. All 7 patients were initially seen with nasal obstruct ion or epistaxis and underwent surgical resection. The period of follo w-up was from 3 months to 14 years (mean 54 months) for 7 patients. Th ree patients had recurrent disease after 3, 5, and 10 years. The first 2 were known to have been originally treated by polypectomy. One pati ent required adjuvant radiotherapy for metastatic disease and local ex tension. One patient was initially seen with tumor-induced osteomalaci a which dramatically improved following resection of the lesion. The i mmunohistochemical profile revealed strong expression of vimentin in 7 /7 cases, and of factor XIIIa in 4/7 cases; tumor cells did not expres s the other markers studied. Conclusions. 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 w ell as lack of expression of other markers, is consistent with the dia gnosis of HPC, which still remains in the domain of histopathology. (C ) 1996 John Wiley & Sons, Inc.