[Cystic adventitial degeneration of the popliteal artery. Rare cause of intermittent claudication in middle-aged adults].

We report on a 36-year old male patient with clinically prolonged intermittent claudication of the right leg. An operative specimen measuring 8.0 cm of the A. poplitea was sent for examination, which was sheathed by an aneurysmal cyst having a maximal diameter of 1.5 cm. Examination under the light microscope showed an incomplete septated ganglion-like cystic formation with flat connective tissue-like cells or even larger histiocytoid cell elements as inner lining. Immunohistochemically, the cells on the inner lining of the cyst showed to be strongly positive to macrophage marker PG-M1, KP1 and Ki-Mp1. The endothelium of the vessels of the wall of the cyst showed a marked expression of cytokeratin 18. Immunohistochemically as well as in conventional histology, there are general parallels between cysts in cystic adventitial degeneration, ganglia and normal synovia as the two last mentioned tissues also show an expression of cytokeratin 18 at the endothelia of smaller vessels as well as an expression of macrophage-associated antigens on cells of the inner lining. Aetiopathologically, the cysts developing in the course of the disease are rather adventitial ganglia.