S1721 A Rare Finding in the Colon: Undifferentiated Pleomorphic Sarcoma

Abstract

Introduction: Undifferentiated pleomorphic sarcoma (UPS) is a rare and incompletely understood condition that commonly appears in the extremities and retroperitoneum. Involvement of the bone and digestive organs is rare. We describe the case of a 78-year-old man who was incidentally diagnosed with UPS of the colon after workup of uncontrolled lower back pain. Case Description/Methods: A 78-year-old man with extensive tobacco use initially presented to his primary care provider with intractable back pain and a 10lb weight loss. His exam was notable for paraspinal muscle tenderness, but otherwise unremarkable. A subsequent computed tomography (CT) abdomen and pelvis was negative. Given these findings and a suspicion for a musculoskeletal diagnosis, he was treated conservatively. Despite initial therapies, he experienced no clinical improvement. Further imaging with magnetic resonance imaging (MRI) of the spine showed a pathologic fracture of T12 and metastatic vertebral disease causing spinal cord compression. A follow up CT showed pulmonary nodules at the lung bases also concerning for metastatic disease. A set of follow up labs showed an elevated carcinoembryonic antigen (CEA) level of 7.4 ng/mL. He was referred to gastroenterology for expedited colonoscopy and malignancy workup in the setting of an elevated CEA. Colonoscopy revealed one 5-9 mm sessile cecal polyp. Cold snare removal of the polyp was unsuccessful because of resistance and the firmness of the lesion. A biopsy was obtained instead. While awaiting pathology, he underwent decompressive laminectomy and spinal stabilization with tumor biopsy of T12 for further neoplastic workup. Pathology of both the cecal polyp and the T12 intervertebral disc revealed high-grade UPS. Given the extent of disease, palliative radiation and chemotherapy were offered however the patient passed away shortly thereafter. Discussion: UPS is a rare and aggressive neoplasm; diagnosis is challenging because patients are often asymptomatic unless there is nerve involvement and because of its rapid development. Our patient presented with back pain which was attributed to a musculoskeletal ailment. Upon further investigation with a colonoscopy and biopsy, UPS was discovered. Although gastrointestinal metastasis is rare, it is important to consider a broad differential when a benign appearing polyp cannot be excised in a standard fashion.