The sentinel polyp: high-grade sarcoma revealed after colonic polypectomy

An 87-year-old man presented with malaise, anorexia and postprandial vomiting for 3 days. At presentation the patient was hypotensive and tachycardic, without any other relevant findings. Laboratory workout showed a normocytic normochromic anemia of 4.9g/dl. No hematic losses from the gastrointestinal tract were described or seen. The patient underwent a colonoscopy to study the anemia and an 18mm semi-pedunculated polyp in the descendent colon was found and excised. A whole-body tomography performed during hospitalization showed multiple nodular lesions in the lungs, pleura, peritoneum and left gluteal muscle compatible with metastatic disease. The polyp histological examination was finally compatible with a high-grade undifferentiated sarcoma. Patient died during hospitalization due to disease progression and multiple complications. Colorectal sarcomas are a very rare group of mesenchymal tumours, accounting for 0,1% of all colonic cancers [1]. They usually present as a high grade and aggressive tumour and are often located in the colon (70%) comparing with the rectum. Metastization is common and more often to the liver, peritoneum and lung. Curative treatment depends on surgical resection without need of extensive lymphadenectomy due to its rare lymphatic dissemination, but prognosis is usually poor [2]. Even so, the polyp described probably reflects a metastatic lesion of an extra-colonic sarcoma and not the primary sarcoma itself. Extrapulmonary metastases, namely intra-abdominal metastases, of musculoskeletal sarcomas are rare and are associated with even poorer prognosis [3]. There are few published papers describing the presence of colonic metastases since their implantation is usually subepithelial.