Carcinoid Tumor of the Duodenum Presenting as Iron Deficiency Anemia

Carcinoid tumors are slow-growing tumors that typically occur in the gastrointestinal (GI) tract, lungs, and other endocrine glands. They are commonly discovered incidentally and usually cause no symptoms. When symptomatic, they tend to present with vague abdominal pain and may lead to carcinoid syndrome after metastasis to the liver. Such tumors rarely present with GI bleeding and thus rarely lead to iron deficiency anemia. In this report, we present an uncommon case of a 71-year-old male who presented with fatigue, weakness, intermittent rectal bleeding, and black stools. He was vitally stable but cachectic. Laboratory studies revealed iron deficiency anemia of unknown origin. Initially, a colonoscopy was performed, which only revealed internal hemorrhoids, so an upper endoscopy was scheduled. Upper GI endoscopy revealed a bleeding duodenal nodule in the upper half of the duodenum that was biopsied. Immunohistochemistry revealed a duodenal carcinoid tumor. The lesion was resected endoscopically as the patient was unfit for surgery due to concurrent comorbidities. Abdominal imaging showed no signs of liver metastasis. The patient was followed periodically by the gastroenterology clinic to ensure no recurrence or metastasis, but he eventually succumbed to other comorbidities. This case highlights the challenges in diagnosing and managing this rare presentation in a significantly ill patient with multiple comorbidities. Upon reviewing the literature, we found that it was uncommon for carcinoid tumors of the GI tract to present with bleeding or anemia. Of those reported in the literature to have caused bleeding, the majority were in the stomach or ileum. To the best of our knowledge, this is the first reported case of a duodenal carcinoid tumor presenting with iron deficiency anemia.