Masson's Tumor Masquerading as a Papillary Adenocarcinoma on Fine Needle Aspiration Cytology: A Case Report.

Intravascular papillary endothelial hyperplasia, previously known as Masson's tumor, is a relatively uncommon reactive endothelial proliferation that occurs most commonly in the vessels of the head, neck, and extremities. We report a case of intravascular papillary endothelial hyperplasia in the neck in a 40-year-old female that was misdiagnosed as papillary adenocarcinoma on fine needle aspiration. The cytologic picture of intravascular papillary endothelial hyperplasia is diverse, making a pinpoint diagnosis of this entity difficult on fine needle aspiration.