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

Area of Science:

• Oncology
• Gastroenterology
• Pathology

Background:

• Colorectal sarcomas are rare mesenchymal tumors, comprising 0.1% of colon cancers.
• They typically present as aggressive, high-grade tumors, often in the colon rather than the rectum.
• Metastasis is common, frequently involving the liver, peritoneum, and lungs.

Observation:

• An 87-year-old male presented with malaise, anorexia, and vomiting, with hypotension and tachycardia.
• Laboratory findings revealed severe normocytic, normochromic anemia (4.9 g/dL).
• Colonoscopy identified an 18mm semi-pedunculated polyp in the descending colon, which was excised.

Findings:

• Whole-body tomography revealed multiple nodular lesions in the lungs, pleura, peritoneum, and gluteal muscle, indicative of metastatic disease.
• Histological examination of the excised polyp confirmed a high-grade undifferentiated sarcoma.
• The colonic polyp was likely a metastatic lesion from an extra-colonic sarcoma, not a primary colorectal sarcoma.

Implications:

• Extrapulmonary metastases, particularly intra-abdominal ones, from musculoskeletal sarcomas are uncommon and associated with a worse prognosis.
• Colonic metastases from sarcomas are rarely documented due to their typical subepithelial implantation.
• This case underscores the aggressive behavior and metastatic potential of rare colorectal sarcomas, even when presenting as seemingly localized polyps.