Clinical and chemical characterization of an adventitial popliteal cyst.

We present further evidence that adventitial cysts of the popliteal artery are ganglions, based on studies of a lesion found in a 51-year-old man. The cyst was located entirely within the adventitia, lacked a cellular lining, and did not communicate with either the arterial lumen or the synovial space. The contents were gel-like and composed of 1.64 gm of hyaluronic acid and 0.20 gm of protein per dl. This material did not possess boundary-lubricating ability in a test system that slides natural latex rubber against glass. The histologic appearance, chemical composition, and absence of lubricating ability more closely resemble the characteristics of ganglions. These findings suggest that the cyst was not synovial but rather ganglionic in origin.