Metastatic pleural mesothelioma presenting as ulcerated submucosal colonic nodules

Malignant pleural mesothelioma is a rare and aggressive malignancy associated with poor prognosis. Although it typically spreads through local invasion, distant metastasis to the gastrointestinal tract is uncommon, and colonic involvement is particularly rare. We report a case of metastatic pleural mesothelioma presenting as ulcerated submucosal nodules in the colon. The patient had previously elected active surveillance for known malignant pleural mesothelioma because of poor performance status and multiple medical comorbidities. Approximately 18 months after diagnosis, he was hospitalized with rectal bleeding and diarrhea. Colonoscopy revealed ulcerated submucosal nodules within the colon, and histopathologic evaluation of biopsy specimens demonstrated colonic mucosa infiltrated by malignant mesothelioma. Systemic therapy was not recommended for bleeding control given the patient's overall clinical condition. Management consisted of supportive care, including one packed red blood cell transfusion and serial hemoglobin monitoring. While prior reports describe colonic metastases presenting as polyps or intussusception, this case highlights an atypical manifestation of mesothelioma involving ulcerated submucosal colonic nodules. Recognition of this rare presentation may aid clinicians evaluating gastrointestinal bleeding in patients with mesothelioma.