Clinicopathologic features and prognostic factors of extrapleural solitary fibrous tumor

Extrapleural solitary fibrous tumor (ESFT) is a rare tumor and its prognosis features are not clear. In this study, the clinical manifestations, imaging characteristics, and pathology features of ESFT were analyzed. Long-term survival (LTS) was analyzed in detail. The histological characteristics and immunohistochemistry expression profiles were compared between, before, and after relapse. Of 29 ESFT, six patients (20.7%) developed recurrence and metastasis to other organ. Cohort median follow-up was 75 months, and the median disease free survival was 111 months. Both the primary and metastatic tumor had similar imaging features especially a single focal metastatic cases. ESFT was found to be well circumscribed and most primary tumors were separated from the peripheral tissue by tumor capsule. Compared with the primary tumor, metastatic SFT was not well circumscribed. The high cell density and atypia; perivascular growth pattern of cells; increased karyokinesis can be found in the tumors. Immunohistochemical staining indicated that the metastatic tumor revealed abnormal expression of P53 and higher Ki67 index. There was no significant difference between the primary ESFT and metastatic tumor both in clinical and radiological manifestation. We found that tumor size larger than 10 cm, incomplete tumor capsule, more than 2 mitosis figures per high power field, Ki67 index larger than 3% and overexpression of P53 were important pathologic risk factors of recurrence and/or metastasis of ESFT. Metastasis of ESFT may present itself over a decade following the surgery. Clinical follow-up is imperative for early detection of tumor relapse and metastasis.