A Rare Case of Duodenal Adenocarcinoma With Brain Metastasis.

Small bowel malignancies are relatively rare, accounting for only 3% of all gastrointestinal cancers. Duodenum is the most common location among small bowel cancers, followed by Jejunum and then Ileum. Duodenal adenocarcinoma produces vague symptoms, leading to late presentation and a poor prognosis compared to similarly staged colon cancer. It is rare to have brain metastasis in duodenal adenocarcinoma, and not many case reports have been reported. Only approximately 6% of patients with gastrointestinal malignancy have brain metastasis. Here, we present a case of a 64-year-old female patient diagnosed initially with stage IV duodenal adenocarcinoma presenting with duodenal mass, abdominal lymphadenopathy, and liver metastasis. She had excellent systemic control for over two years with systemic chemotherapy, with a close to complete response on follow-up imaging. She presented with a 2 cm left frontal mass biopsy consistent with duodenal adenocarcinoma metastasis. She underwent resection of the left frontal tumor and gamma knife to the resection cavity. She continues to have good systemic control of disease. This case highlights the rare possibility of brain metastasis with duodenal adenocarcinoma, especially in patients who have good systemic control with chemotherapy.