# Adenocarcinoma of the Lung With Metastasis to the Small Intestine: Case Report

## TL;DR

A lung cancer patient developed severe anemia due to metastasis in the small intestine, highlighting the need to consider gastrointestinal metastasis in such cases.

## Contribution

This case report highlights the rare occurrence of lung adenocarcinoma metastasis to the small intestine and its presentation as unexplained anemia.

## Key findings

- A lung adenocarcinoma patient presented with anemia caused by metastasis to the small intestine.
- Biopsy confirmed metastatic tumor cells in the jejunum matching those in the lung.
- Chemo-immunotherapy improved the patient's condition over two years.

## Abstract

A 40‐year‐old man presented with dyspnea and dizziness. He was found to have severe anaemia and computed tomography revealed a mass in the right upper lobe of the lung. Despite a positive test for faecal occult blood, the source of bleeding could not be identified. The patient was diagnosed with adenocarcinoma of the lung, cT3N2M0 stage IIIB. Initially, he received chemotherapy consisting of cisplatin and docetaxel and thoracic radiotherapy. However, a few days after the initiation of chemoradiotherapy, his anaemia worsened. Capsule endoscopy revealed multiple ulcers and erosions in the intestinum jejunum. A biopsy using double‐balloon endoscopy revealed poorly differentiated tumour cells with similar characteristics to those in the lung. The clinical stage was modified to T3N2M1c stage IVB. The patient was treated with chemo‐immunotherapy consisting of carboplatin, paclitaxel, ipilimumab, and nivolumab. He is currently doing well after completing 2 years of treatment.

We reported a case of adenocarcinoma of the lung with severe anaemia due to metastasis to the small intestine. Gastrointestinal metastasis should be considered when unexplained anaemia is present in patients with lung cancer. A thorough examination should be conducted to detect the anaemia.