Solitary fibrous tumor of the central nervous system: a clinicopathologic study of 24 cases

Solitary fibrous tumor is a rare, spindle-cell benign mesenchymal neoplasm and has a high recurrence rate. In this study, we reviewed our experience in the diagnosis and treatment of 24 patients with central nervous system solitary fibrous tumors.

Clinical data were retrieved from the medical records. Prognosis was assessed by clinic service and telephone interview. The specimens were stained with hematoxylin and eosin. Immunohistochemistry for CD34, CD99, EMA, HMB-45, Bcl-2, vimentin, GFAP, S-100, MBP, CK and MIB-1 was performed in all cases. Distributions of time to progression and recurrence were estimated using the Kaplan­Meier method and compared using the log-rank test.

The 24 patients included 13 men and 11 women with a median age of 49.0 years. The most frequent initial symptoms were headache, dizziness, unstable walk and hearing loss. The most common location was cerebellar pontine angle (n = 6). Surgery reached gross total removal for 18 patients but subtotal removal for six patients on initial operation. Histopathologic examination showed spindle to oval cells were disposed in wavy fascicles between prominent, eosinophilic bands of collagen. Dense bands of collagen appeared in cross section as minute nodules that separated individual tumor cells. Cellular areas with a partial hemangiopericytoma pattern were noted in six cases. Atypical presentations were shown on initial operation in three cases. CD34, CD99 and vimentin were 100% positive; but EMA, CK, MBP, HBM-45 and GRAP were 100% negative. The positive in Bcl-2, RF and S-100 was 89%, 85% and 26%, respectively. Follow-up information was available for 23 patients. The median follow-up period was 36.0 months. Nine patients recurred and one patient died from the progression. Incomplete surgical resection was significantly associated with recurrence (p = 0.010). MIB-1 labeling index in recurrence was higher than in no recurrence (6.0% versus 3.4%, p = 0.029). All treated with subtotal removal only had subsequent tumor recurrence or progression; however, the two patients who were administered adjuvant radiosurgery after subtotal removal did not recur or progress. Adjuvant radiosurgery seemed to improve the prognosis (p = 0.028).

Solitary fibrous tumor is a rare mesenchymal tumor with a propensity to recur. The most affected area is the cerebellopontine angle. Immunohistochemistry should be used to differentiate solitary fibrous tumor from other tumors. The extent of resection, MIB-1 labeling index and some anaplastic features might be predictive for recurrence. Postoperative radiosurgery might be an option in incompletely resected solitary fibrous tumor. Regular and long-term follow-up remains mandatory to monitor recurrence.