Synchronous carcinoma of the anal canal and stomach presenting as severe anemia: a case report

Synchronous primary malignancies of the gastrointestinal tract are uncommon, and the combination of anal canal squamous cell carcinoma with gastric adenocarcinoma is exceptionally rare. A 56-year-old female presented with bleeding per rectum and easy fatigability. Examination revealed severe pallor. Laboratory evaluation showed profound anemia (hemoglobin 5 g/dL). Upper gastrointestinal endoscopy and colonoscopy revealed an ulceroproliferative growth in the antrum of the stomach and a mass lesion involving the anal canal. Biopsy confirmed gastric adenocarcinoma and anal canal squamous cell carcinoma. Positron emission tomography-computed tomography (PET-CT) demonstrated locally advanced anal canal disease with regional nodal involvement and an 18 F-fluorodeoxyglucose (FDG)-avid gastric lesion with distant metastases. The patient was managed with systemic chemotherapy (CAPOX regimen). This case highlights the importance of thorough evaluation of patients presenting with rectal bleeding and anemia, as synchronous malignancies may coexist and significantly impact management.