Proliferation index as a prognostic marker in hemangiopericytoma of the head and neck

BACKGROUND: Hemangiopericytoma (HPC) of the head and neck is a rare neoplasm whose biologic behavior is difficult to predict by means of conventional histologic parameters. METHODS: H & E-stained sections from 12 cases of HPC were reviewed. Proliferation index was assessed using an immunoperoxidase stain for MIB-1 (Ki-67). RESULTS: The study group consisted of 4 adult men, 5 adult women, and 1 infant male. Necrosis, hypercellularity, and pleomorphism were found in 1, 5, and 6 case(s), respectively. The mitotic index per 10 high power fields varied from 0-1 to 15. Proliferation indices using MIB-1 ranged from 2.6% to 52.5%. Clinical follow-up revealed 3 cases with recurrence all possessing proliferation indices of approximately 10%. CONCLUSIONS: Standard histomorphologic features may be inadequate predictors of clinical outcome. A proliferation index of 10% or greater may indicate a more aggressive subset of HPC of the head and neck.