Haemangiopericytoma

Introduction

Haemangiopericytomas are very common mesenchymal tumours in middle-aged or older dogs. It is more common in large breed dogs but there is no sex predilection.

Such tumours occur rarely in cats.

The origin of these tumours is uncertain, although they seem to be associated with the periphery of blood vessels and they may be related to Peripheral Nerve Sheath Tumours.

Clinical signs

Tumours are usually solitary, arise in the subcutis around joints of limbs, and are multilobulated and inflitrative.

Their gross appearance varies, from white/gray to red, and rubbery to fatty.

Diagnosis

Fine Needle Aspiration should be performed.

Characteristic cytological features include: perivascular whorls of fusiform cells. Cells may also be arranged in interlacing bundles. In some tumours there is a patchy mucinous matrix.

The tumour may be well demarcated from adjacent structures, but it often invades along fascial planes leading to recurrences.

The mitotic index is the key prognostic indicator in these tumours, and the usually low metastatic potential increases with each recurrence.

It can be difficult to distinguish these tumours from Peripheral Nerve Sheath Tumours.

FNA of the draining lymph node may also be performed to stage the tumour.

Treatment

Aggressive initial surgery is the best treatment for haemangiopericytomas. Wide margins may be difficult to obtain due to the location on limbs. Recurrence following surgery is common.

Radiotherapy can also result in tumour control and longer survival times. Amputation may also have to be considered.

Chemotherapy is not effective.

References

Meuten, D. (2002) Tumors in Domestic Animals Wiley-Blackwell

Freeman, K. (2007) Self-assessment colour review of: Veterinary cytology Manson Publishing