Solitary fibrous tumor and haemangiopericytoma

Soft-tissue tumors with haemangiopericytoma (HPC)-like growth patterns can now be divided into three categories: (1) The solitary fibrous tumour (SFT) group with its variants; (2) lesions showing clear evidence of myoid/pericytic differentiation and corresponding to "true" HPCs (myopericytoma/glomangiopericytoma and a subset of sinonasal HPCs); (3) neoplasms that occasionally display HPC-like features (e.g. synovial sarcoma). In this study 268 intrathoracic and extrathoracic SFTs from the German consultation and reference center of soft tissue tumors in Jena were evaluated and analyzed immunohistochemically with antibodies CD34, Bcl-2, CD99, SMA, S100, PanCK and Ki-67. Furthermore, SFTs were categorized into the newly proposed SFT designation: Fibrous variant, cellular variant (more than 90% hypercellularity), fat-forming variant, giant cell-rich variant and malignant SFTs. This article should provide insights into the diagnosis of this entity with emphasis on the new international standard.