[AN ISOLATED INTERNAL ARTERY ANEURYSM WITH COMPLETE THROMBOTIC OCCLUSION FOR WHICH PREOPERATIVE DIAGNOSIS WAS DIFFICULT: A CASE REPORT].

A 74-year-old man was incidentally discovered during treatment of prostate cancer to have a pelvic tumor, measuring 8 cm in diameter. Enhanced abdominal computed tomography (CT) showed a roundish-shaped hypovascular solid tumor compressing the left internal iliac artery to the inner back side. Values on endocrinological examination were within normal ranges. The tumor was suspected to be chronic abscess, angiosarcoma, or gastrointestinal stromal tumor (GIST) or neurogenic tumor, but no definitive diagnosis was able to be established before operation. During laparotomy, given its location relative to the internal iliac artery wall, the tumor was extracted by sacrificing periphery of the artery. The pathological diagnosis was an internal artery aneurysm with complete thrombotic occlusion. Isolated internal iliac aneurysm is rare, and this is the first case which resulted in complete thrombotic occlusion.