Diagnostic challenge of underlying colon cancer revealed by atypical presentation: two case reports and literature review.

Introduction and importance: Foreign body ingestion is usually benign but may rarely lead to bowel obstruction or perforation. Foreign bodies often become impacted at sites of luminal narrowing, including colonic tumors. The incidental discovery of underlying malignancy in this context is exceptional and represents a diagnostic challenge. These cases illustrate an atypical presentation of colon cancer and highlight the importance of considering malignancy even when an apparent cause of obstruction is identified. They contribute to the surgical literature by emphasizing the need for careful intraoperative assessment and histopathological evaluation. Presentation of case: Two women, aged 56 and 38 years, presented with large bowel obstruction. Computed tomography showed colonic distension with a sigmoid intraluminal foreign body; in the second case, regular wall thickening, suggestive of a reactive change to the foreign body, was observed without features of malignancy. Differential diagnoses included foreign body obstruction and colonic tumor. Emergency laparotomy revealed a sigmoid tumor with an impacted foreign body in both cases. Hartmann's procedure was performed, and histopathology confirmed colonic adenocarcinoma. Postoperative outcomes were uneventful. Clinical discussion: Foreign bodies tend to become impacted at sites of narrowing, including colonic tumors, where they may precipitate acute obstruction and reveal malignancy. Emergency presentations of colonic cancer are associated with higher morbidity and often require staged surgery. These cases illustrate the difficulty in distinguishing isolated foreign body obstruction from tumor-related obstruction. Conclusion: Foreign body-induced obstruction may reveal occult colonic cancer. A high index of suspicion, prompt surgery, careful exploration, and histopathological evaluation are essential for accurate diagnosis and management.