Abstract
The major causes of rare extracranial carotid artery aneurysms are arteriosclerosis, trauma, and radiation therapy. Here, we describe a patient with an extracranial carotid artery aneurysm caused by a myeloproliferative neoplasm. A 67-year-old woman underwent excision of an irregularly shaped aneurysm in the left common carotid artery and a saphenous vein graft without major complications. The pathologic findings revealed abscess formation and atypical megakaryocyte infiltration, which was also seen in her bone marrow, indicating that the aneurysm was caused by a myeloproliferative neoplasm.