Solitary fibrous tumor: a clinicopathological study of 110 cases and proposed risk assessment model

Abstract

Solitary fibrous tumor represents a spectrum of mesenchymal tumors, encompassing tumors previously termed hemangiopericytoma, which are classified as having intermediate biological potential (rarely metastasizing) in the 2002 World Health Organization classification scheme. Few series have reported on clinicopathological predictors with outcome data and formal statistical analysis in a large series of primary tumors as a single unified entity. Institutional pathology records were reviewed to identify primary solitary fibrous tumor cases, and histological sections and clinical records reviewed for canonical prognostic indicators, including patient age, tumor size, mitotic index, tumor cellularity, nuclear pleomorphism, and tumor necrosis. Patients (n ¼ 103) with resected primary solitary fibrous tumor were identified (excluding meningeal tumors). The most common sites of occurrence were abdomen and pleura; these tumors were larger than those occurring in the extremities, head and neck or trunk, but did not demonstrate significant outcome differences. Overall 5-and 10-year metastasis-free rates were 74 and 55%, respectively, while 5-and 10-year disease-specific survival rates were 89 and 73%. Patient age, tumor size, and mitotic index predicted both time to metastasis and disease-specific mortality, while necrosis predicted metastasis only. A risk stratification model based on age, size, and mitotic index clearly delineated patients at high risk for poor outcomes. While small tumors with low mitotic rates are highly unlikely to metastasize, large tumors Z15 cm, which occur in patients Z55 years, with mitotic figures Z4/10 high-power fields require close follow-up and have a high risk of both metastasis and death.

Nuclear expression of STAT6 distinguishes solitary fibrous tumor from histologic mimics

“…The majority of SFTs that behave aggressively show histological features of malignancy, such as 44 mitoses per 10 HPF and hypercellularity, but benign-appearing SFTs can Modern Pathology (2014) 27, 390-395 STAT6 in SFT also rarely give rise to metastases. 17 Histologically, SFT may resemble some benign soft tissue tumors (eg, soft tissue perineurioma, desmoid fibromatosis, spindle cell lipoma, and cellular angiofibroma); soft tissue tumors with potential for locally aggressive behavior (eg, desmoid fibromatosis); and spindle cell sarcomas (eg, malignant peripheral nerve sheath tumor, dermatofibrosarcoma protuberans, and monophasic synovial sarcoma). The immunohistochemical profile of SFT using conventional markers is relatively nonspecific, with CD34 expression being the most consistent finding reported to date, present in 95% of cases.…”

Solitary fibrous tumor of the vagina with potentially malignant features: a case report and review of the literature

“…In a recent article published by Demicco et al, the authors clinicopathologically analyzed 110 cases of solitary fibrous tumor (primary soft tissue: 79 cases, and pleural solitary fibrous tumors: 31 cases), and suggested a risk stratification model based on age, size, and mitotic index (10). According to this model a 3-tiered model stratifying the patients by overall risk of metastasis (low, moderate, or high) was developed.…”

Update on Select Benign Mesenchymal and Meningothelial Sinonasal Tract Lesions

“…Therefore, there is an overall good behavior with low local recurrence rate, different from other anatomic sites [39]. Although not reported in the sinonasal tract, SFTs in patients [55 years, with large tumors ([15 cm), with necrosis, increased mitotic activity and/or pleomorphism or incomplete resection are designated as ''malignant'' or ''dedifferentiated'' SFT [40,41], associated with metastasis and disease-specific mortality [42]. Treatment of sinonasal tract SFTs is usually by complete excision or by wide excision.…”