A Masson's tumor is a benign, intravascular tumor, typically located in the fingers. Histologically, a Masson's tumor is characterized by an intravascular endothelial papillary projection associated with thrombi, without atypia or necrosis. The CD 31 and CD 34 stains are the most efficient immunohistological markers to identify the vascular origin.

A 54-year-old man presented with a right lateral neck mass for 3 weeks. The CT scan of the neck showed an oval, well-circumscribed cystic mass, measuring 20mm×9mm, situated over the right sternocleidomastoid muscle, with a peripheral vessel draining into the right anterior jugular vein. The mass was excised surgically, and a pathological report indicated a thrombosed material inside the lumen of a small vein with a differentiated papillary structure; neither nuclear atypia nor necrosis were seen. The patient had an uncomplicated recovery and completed 8 months of follow-up appointments without any evidence of recurrence.

Intravascular papillary endothelial hyperplasia (IPEH) can be differentiated from angiosarcoma by lack of extension to the perivascular tissue and absence of necrosis and atypia. The pathogenesis is still unknown; surgical excision is the method of treatment. This is an extremely rare presentation of Masson's tumor.