Upper Extremity Arteriovenous Malformation Masquerading as a Biceps Ganglion Cyst.

A 71-year-old male presented to the clinic with two multiloculated cystic masses located over the distal bicep of his left upper extremity, causing discomfort when flexing the extremity. Referral and point-of-care ultrasound at an outside location suggested cystic masses that were consistent with that of a ganglion cyst. Physical exam and clinical presentation were also consistent with this diagnosis. Due to the patient's symptomatic presentation, surgical intervention was proposed, and the patient consented. Intraoperatively, it was discovered that the patient's mass was unexpectedly due to an arteriovenous malformation, revealing the importance of careful workup for cystic masses presenting in unusual locations.