Intravascular papillary endothelial hyperplasia (Masson's tumor) manifesting as a lateral neck mass

Intravascular papillary endothelial hyperplasia is a benign lesion of vascular origin that is caused by an excessive proliferation of endothelial cells in normal blood vessels or vascular malformations. We report the case of a 26-year-old man who had such a lesion deep within the soft tissues of his neck. Imaging studies revealed a 6-cm-diameter mass, with its epicenter in the right retromandibular space. The mass extended into the right parapharyngeal space and compressed the pharynx. The mass was excised, and the patient recovered uneventfully. We discuss the management of this lesion, with emphasis on radiologic and histologic assessment and the differential diagnosis.