Pleomorphic hyalinising angiectatic tumour of soft parts

Definition

This is a tumour of uncertain lineage composed of clusters of ectatic thin-walled vessels, lined by fibrin, within a pleomorphic spindle cell stroma with an inflammatory cell component but lacking mitotic activity. The contrast between the pleomorphism and the lack of mitoses is a diagnostic clue.

Epidemiology

This rare tumour occurs with equal frequency in adults of either gender.

Clinical features

This tumour occur in the subcutis, with more than 50% of cases in the lower extremity. A few cases occur in deep soft tissues.

Histopathology

The tumour is not encapsulated. There are clusters of ectatic thin-walled vessels of variable size. A layer of fibrin separates the endothelium from the vessel wall. Intravascular thrombosis is common. The stroma shows hyalinisation and contains spindle or round cells with pleomorphic hyperchromatic nuclei. There are frequently intra-nuclear inclusions. Mitoses are very scanty. A variable mixed inflammatory cell infiltrate may be present. There is frequently haemosiderin deposition.

Immunohistochemistry

	CD34	occasionally positive0
	Vimentin	positive0
	EMA	may be positive0
	S-100	negative0
	Actin	negative0
	Desmin	negative0
	Cytokeratin	negative0
	Factor VIII RA	negative0
	CD31	negative0

Differential diagnosis

• Ancient Schwannoma

• Melanotic Schwannoma

• Haemangioma

• Malignant fibrous histiocytoma / pleomorphic sarcoma

Prognosis

About half of tumours recur locally but metastases are unknown.

References

⁰ Tumours of Soft Tissues and Bone. WHO Classification of Tumours. IARC Press 2002.

¹ Tos AP Classification of pleomorphic sarcomas: where are we now? Histopathology 2006; 48:51-62

This page last revised 6.2.2006.

©SMUHT/PW Bishop