Pathological Features and Clinical Course in Patients With Recurrent or Malignant Orbital Solitary Fibrous Tumor/Hemangiopericytoma.

Purpose: A risk assessment score for metastasis based on age, tumor size, and mitotic figures has been suggested for nonorbital solitary fibrous tumor (SFT)/hemangiopericytoma. The authors herein examine the clinicopathological features of recurrent and metastatic orbital SFT and evaluate the existing risk assessment score for orbital SFT. Methods: The American Society of Ophthalmic Plastic and Reconstructive Surgery Oncology Database was queried for patients with recurrent or malignant orbital hemangiopericytoma/SFT. The medical records were reviewed for clinical and pathologic findings, treatments, and outcomes. Results: Eight patients from 3 institutions were identified with recurrent orbital hemangiopericytoma/SFT. Median age at diagnosis was 59 years, and 4 patients were women. The mean size of tumor was 2.1 +/- 1.1 cm. All patients were initially treated with surgery and experienced local recurrence after a median of 4 (range 0.5-10) years. Five patients were treated with orbital radiation. Two patients also developed distant metastases and eventually died of their disease. Median Ki-67 was 5% (range 1-65%) and 5 mitotic figures/10 high-power fields (range 2-30). The previously described risk stratification model for nonorbital SFT did not correlate with the propensity to develop metastases in this cohort; however, both patients with distant metastasis had >4 mitotic figures /10 high-power fields. Conclusions: In this cohort of recurrent orbital hemangiopericytoma/SFT, median time to recurrence was 4 years underscoring the importance of careful continued follow-up. The current risk stratification models have limited use for orbital lesions, mostly due to the fact that orbital SFTs are smaller than even the smallest size criteria in this risk assessment model.