A case of Masson's vegetant, intravascular haemangioendothelioma presenting in a large neck vein.

Masson's vegetant intravascular haemangioendothelioma is a rare, benign, intravascular tumour. It is often associated with a pre-existing vascular process such as a pyogenic granuloma or a haemangioma. The clinical diagnosis is usually that of a vascular lesion or of a cyst. This is the first report of such a lesion presenting in a large neck vein. It is important to recognize the existence of this tumour as it is invariably benign, and local excision is curative.