Haemangiopericytoma--an unusual tumour--a report of 5 cases.

Haemangiopericytoma (HPC) has remained a controversial entity ever since its first description. The main histological criterion to diagnose this entity is the characteristic vascular pattern highlighted by the reticulin stain. Since this pattern can be present in several other connective tissue tumours, it is basically a diagnosis of exclusion. Electron microscopy has however been helpful in some cases.