Solitary Fibrous Tumours

Abstract

Solitary fibrous tumors (SFT) are unusual ubiquitous soft tissue tumors of intermediate biological potential with a low risk of metastasis. SFT usually occur in middle-aged adult aged 20–70 years. Most tumours are well-delineated slow growing mass while some malignant tumours are more infiltrative. On microscopy, typical SFT show a patternless architecture with a combination of hypocellular and hypercellular areas. The hypercellular areas contained sheets of cells with thin-walled branching “haemangiopericytoma-like” vessels. In 2013, two different teams simultaneously reported a NAB2-STAT6 fusion transcript in most SFTs whatever their localization. Remarkably, the NAB2-STAT6 fusion eventually leads to nuclear translocation of the C-terminal portion of STAT6, which can then be detected using immunohistochemistry. IF nowadays diagnosis is easy with immunohistochemistry and or genetics data, clinical or histopathological pronostic factors are more controversial. Recent studies proposed a risk stratification for local and metastatic recurrence with a combination of clinical parameters: age, location, size of the tumour and histological features: mitotic index and necrosis. Surgery is the mainstay treatment though complementary therapies are probably necessary for some patients since late recurrences are reported by several studies. The overall survival rate at 10 years is about 75% for patients without metastasis at the time of diagnosis but it is only 50% at 20 years. This confirms the poor prognosis of these tumors in the long term and the need for protracted follow-up.