SIR 2006 Film Panel Case: Spindle Cell Tumor of the Thigh

Abstract

A 65-year-old Middle Eastern woman initially presented with left-sided pain in the pelvis and thigh and was evaluated for venous insufficiency. Computed tomography was performed, optimized to look for pelvic or ovarian varices. None were present. An enhancing contralateral thigh lesion (Fig 1) was found incidentally, only partially imaged. Ultrasonography (US) might have revealed the true nature of the lesion, but because the patient had a distant history of right hip dislocation and pelvic trauma, angiography was performed in anticipation of treatment of a pseudoaneurysm. Instead, a well-circumscribed oval hypervascular mass 4 cm 3 cm was discovered. It received its blood supply from the internal iliac artery (Fig 2), with the predominant contribution from the inferior gluteal artery (Fig 3) and secondary supply from internal pudendal artery branches. Even though the patient was asymptomatic and the lesion had a benign angiographic appearance, the differential diagnosis was expanded to include a posttraumatic sarcoma or a tumor related to the sacral nerve. Surgical excision therefore seemed inevitable, and the arterial feeder vessels to the lesion were occluded (Fig 4) with 0.018-inch Tornado platinum embolization coils (Cook, Bloomington, IN) to minimize the risk of hemorrhage and facilitate identification at the time of surgery. A wide surgical resection was performed, and the postoperative course was uneventful. Histologic analysis revealed a very well circumscribed benign spindle-cell tumor with a prominent vascular pattern and large staghorn vessels. There was no discernible necrosis or mitotic activity, and there were variable amounts of adipose tissue. Immunoperoxidase staining was positive for collagen type 4, BCL-2, CD34, and CD99.