Extracranial carotid artery aneurysm.

Although rare, extracranial carotid aneurysms are common enough to be considered in the differential diagnosis of a mass in the neck or posterior pharynx. The unexpected finding of an aneurysm of the carotid artery during the biopsy of a mass in the neck for histologic diagnosis could be catastrophic. The case presented demonstrates the importance of diagnostic imaging of the neck prior to biopsy of a clinically presumed solid mass.