Hemangiopericytoma-solitary fibrous tumour of soft tissue: description of a case showing atypical histological features.

Extrathoracic solitary fibrous tumours have been reported in almost all anatomic sites, but reports of tumours in the extremities or in intramuscular locations, as well as of tumours with atypical histological features and malignant behaviour, are rare. Herein the authors describe a case of hemangiopericytoma-solitary fibrous tumour that arose in the gluteal region of a 47-year-old woman. The tumour showed atypical histological features, such as high cellularity, increased mitotic activity and focal expression of cytokeratins.