Adventitial cystic disease of the popliteal vein: report of a case.

Adventitial cystic disease (ACD), also known as cystic mucoid or myxomatous degeneration, is a rare vascular disease seen mainly in arteries. It is very unusual for these cystic masses to develop in a vein. We report the case of a 56-year-old woman with leg swelling caused by ACD arising in the popliteal vein. The swelling appeared after a long period of standing. Magnetic resonance imaging (MRI) showed a popliteal cystic mass and venography showed disrupted venous flow. We resected the cyst wall without venous reconstruction, after which venous blood flow normalized and her symptoms subsided. To our knowledge, this is only the third documented case of ACD arising in the popliteal vein. A misdiagnosis could easily have been made, since the mass was not obvious on physical examination and the only symptom was intermittent swelling. Thus, it is important to be aware of ACD as a possible diagnosis when examining patients with a swelling in the leg.