Orbital solitary fibrous tumor: a clinicopathologic study of ten cases with long-term follow-up.

Background: Solitary fibrous tumor (SFT) is a rare spindle-cell benign neoplasm and located in orbit. The present research represents case reports of ten patients with orbital SFT.

Method: Prognosis was assessed by clinic service and telephone interview. Clinical data were retrieved from the medical records. Immunohistochemistry for CD34, CD99, EMA, HMB-45, Bcl-2, GFAP, S-100, MBP, CK, and MIB-1 was performed. Distributions of time to progression and recurrence between different operative methods were estimated using the Kaplan-Meier method and compared using the log-rank test.

Findings: The ten patients included six men and four women (range: 19-75 years). The most common initial symptom was painless proptosis (n = 6). After the ten initial surgeries, with four requiring gross total resection (GRT) and six requiring subtotal resection (STR), an additional nine were required to remove recurrent tumors. Eighteen samples were obtained for pathological examination (the third sample for case 4 was not achieved). Cellular areas with partial hemangiopericytoma pattern were noted in four samples (4/18); scarce mitosis was noted in six samples (6/18). All SFTs (18/18) were positive for CD34, CD99 and vimentin, while all SFTs (18/18) were negative for EMA, CK, MBP, HBM-45 and GFAP. Bcl-2 was positive in 13/18 cases, while S-100 was negative in 14/18 cases. The MIB-1 labeling index varied from 1% to 3%. Follow-up was available for nine patients with a median of 88 months. All four patients who underwent GTR on initial operation did not recur; while the five patients who underwent STR recurred. The log-rank test showed that the incomplete surgical resection was significantly associated with recurrence (p = 0.015).

Conclusions: Orbital SFT is a rare mesenchymal tumor and painless proptosis is the most common initial symptom. Immunohistochemistry should be used to differentiate SFT from other tumors. Orbital SFT usually has a non-aggressive histological characteristic, and has a good prognosis if GTR is performed. Postoperative regular and long-term follow-up remains mandatory to monitor recurrence.