Adventitial cystic disease.

Adventitial cystic disease (ACD) is an unusual cystic tumor of blood vessels characterized by the accumulation of mucinous substance in the adventitia of the non-axial blood vessels adjacent to joints. Patients with ACD often suffer from intermittent claudication and/or limb pain, mostly involving the popliteal artery. We report a 30-year-old male who presented with intermittent claudication in his left leg. Angiography showed an obstructive lesion in the left popliteal artery. The lesion was treated successfully by surgical excision followed by graft vessel replacement. ACD involving the popliteal artery was diagnosed by pathologic findings of multiple cysts of the adventitia with external compression and focal narrowing of the vascular lumen. The cysts contained acid mucin and were partially lined by multiple rows of cytologically bland, synovium-like cells with positive immunoreactivity to vimentin and CD68 but negative immunoreactivity to cytokeratin. The histopathologic findings in this case suggest that it was caused by the developmental rests of mucin-secreting mesenchymal cells derived from the knee joint.