Case 5 -

Adventitial Cystic Disease of the Popliteal Artery Alan G. Rose

Clinical History A 25-year-old man presented with symptoms of intermittent claudication of his left lower leg. Arteriography revealed a smooth-walled narrowing of the popliteal artery. The affected segment of the artery was resected and replaced by a graft. His histology shows a classical example of adventitial cystic disease (ACD) of the popliteal artery. The arterial lumen is compressed due to the presence of a unilocular cystic space within the adventitial layer affecting at least 50% of the circumference of the artery. Portion of the cyst is lined by flattened, mesothelial-like cells, but most of the cyst lining is composed of bare collagen. Scanty foamy histiocytes are also noted, but the cyst contents have been lost. A Touton type giant cell was present in one area. Fresh operative hemorrhage is noted alongside the artery. The arterial intima shows focal thickening with fibrous interruption of the internal elastic lamina and a zone of fresh intra intimal hemorrhage. The wall of the adventitial cyst is composed of denser, more hyalinized collagen than the adjacent adventitia and the cyst appears to be collapsed, unlike its tense, expanded condition prior to excision and surgical incision. Medial sclerosis and hyalinization is noted in areas in the parent artery. One level shows obliquely sectioned intima with scanty mural organizing thrombus, that occupies portion of the arterial lumen and accounted for the surgical resection and grafting. Case 5 - Figure 1 - Cystic adventitial disease has produced the space seen in the upper portion of the picture. Portion of the original arterial lumen (with some mural thrombus) is seen below this. Adventitial cystic disease is an idiopathic, cystic accumulation of mucinous material in the adventitia of an artery, possibly related to trauma, ectopic ganglion cyst or "dysplasia." [1] The condition is defined as "a dysplastic lesion of vascular wall, of unknown cause, characterized by the formation of a mucoid cystic mass, with or without a true cellular lining, in or around the adventitia of an otherwise normal blood vessel (artery or vein)". [2] ACD occurs near a joint, 10 times more often in the wall of medium or small arteries (especially the popliteal artery behind the knee joint) than comparable-sized veins. ACD accounts for one in 1200 cases of limb claudication and is 5-8 times more frequent in men, usually manual laborers with a mean age of 40 years (range 10-70 years). The cyst may even envelop the entire circumference of the artery. About 250 cases of ACD have been reported in the literature up to the mid-1990s. On angiography, ACD gives an appearance of a smooth-walled, fluted stenosis, or rarely it may produce total occlusion of the affected artery, which may be displaced laterally or in an anteroposterior direction. Incomplete excision of the "cyst" may lead to its recurrence. In addition to intra-arterial cysts, there may be additional mucinous filled cysts within the adjacent popliteal fossa. Microscopy characteristically shows an encapsulated cystic cavity filled with a gelatinous content that has the staining properties of glycoprotein and acid mucopolysaccharide and may contain collagen fragments with minimal or no inflammatory features around the vessel wall. The cystic structure may be unilocular or multilocular and its inner surface is rarely lined with a flattened cell layer of uncertain origin. The latter finding has led to suggestions that the condition may represent ectopic synovial lining (derived from the neighboring joint or synovial sheath) displaced into the adventitia of the popliteal artery. The lectin-binding pattern of adventitial cystic disease appears to be similar to the reactivity pattern of normal synovium. [1] Rarely, the media may share in the mucinous degeneration. The gelatinous contents of the cyst may be readily evacuated without opening the arterial lumen, but bypass of the lesion may be needed if there is luminal occlusion. Angioplasty is not applicable for the treatment of ACD. Several authors have reviewed ACD of arteries [3, 4] and Lie et al. [5] reported the condition in the lesser saphenous vein. The differential diagnosis includes popliteal entrapment syndromes, atherosclerosis with or without superimposed thrombosis, fibromuscular dysplasia and vasculitis e.g., Buerger syndrome. In the popliteal entrapment syndrome, chronic trauma inflicted by pressure on the arterial wall, leads to a distinctive abnormal development of longitudinal muscle bundles in the arterial media. References Virmani R, Burke A, Farb A. Atlas of Cardiovascular Pathology. Philadelphia, WB Saunders Company, 1996, p 186. Lie JT. Adventitial cystic disease (ACD). In Bloom S (ed), Lie JT, Silver MD (associate eds): Diagnostic criteria for cardiovascular pathology. Acquired diseases. Philadelphia, Lippincott-Raven 1997, pp. 151-152. Flanigan DP, Burnham SJ, Goodreau JJ, Bergan JJ. Summary of cases of adventitial cystic disease of the popliteal artery. Ann Surg 1979; 189: 165-175. Ishikawa K. Cystic adventitial disease of the popliteal artery and of other stem vessels in the extremities. Jap J Surg 1987; 17: 221-229. Lie JT, Jensen PL, Smith RE. Adventitial cystic disease of the lesser saphenous vein (Review). Arch Pathol Lab Med 1991; 115; 946-948.