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WHO Classification of Tumours
Solitary fibrous tumor
Connective, subcutaneous and other soft tissues


Solitary fibrous tumour (STF) is a slowly growing, localized neoplasm histologically characterized by the presence of round to spindle-shaped cells, hyalinized stroma formation, thin-walled branching blood vessels, and thin bands of collagen. Further common features are myxoid change, areas of fibrosis and interstitial mast cells.
STF may arise at any location; roughly 40% are found in subcutaneous tissue. The tumours range in size between 1 and 25 cm and are usually well circumscribed, often partially encapsulated masses. Tumour necrosis and local infiltration may be seen in malignant tumours.
SFTs mainly affect adults between 20 and 70 years (median: 50 years). Most cases are benign, but approximately 10-15% follow an aggressive course, long-term follow-up is thus mandatory. SFT metastasizes most frequently to lung, bone and liver

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Fletcher CDM, Unni KK, Mertens F (Eds.)
World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of Soft Tissue and Bone.
3rd Edition
IARC Press: Lyon 2002


Haemangiopericytoma (HPC) closely resembles cellular areas of solitary fibrous tumour (SFT) and is closely related to, if not synonymous with, SFT. Lipomatous haemangiopericytoma (LHPC) is a rare, slow-growing, non-metastasizing variant composed of mature adipocytes and haemangiopericytoma-like areas which shares many features with SFT. Both lesions occur in similar clinical settings, although LHPC predominates in males (M/F ratio 2:1) and affects preferentially the deep soft tissues of the lower extremity.