# Pulmonary metastasis originating from colonic mucinous adenocarcinoma with a tree-in-bud pattern on computed tomography: A case report

## TL;DR

A case report shows that pulmonary metastasis from colonic mucinous adenocarcinoma can appear as a tree-in-bud pattern on CT scans, which is usually linked to inflammation.

## Contribution

This case highlights the rare occurrence of a tree-in-bud pattern caused by metastatic mucinous adenocarcinoma rather than inflammation.

## Key findings

- Pulmonary metastasis from colonic mucinous adenocarcinoma presented as a tree-in-bud pattern on CT.
- Histopathology confirmed mucus-filled bronchioles in the affected lung segments.
- The tree-in-bud pattern in colon cancer patients with extracellular mucus requires thorough evaluation.

## Abstract

The tree-in-bud pattern, a chest computed tomography (CT) finding, is occasionally associated with malignant tumors. We report a surgical case of pulmonary metastasis from colonic mucinous adenocarcinoma presenting with a tree-in-bud pattern on chest CT. A 50-year-old man underwent surgery for descending colon cancer, which was histopathologically diagnosed as well-differentiated mucinous adenocarcinoma. During follow-up after adjuvant chemotherapy, chest CT revealed nodules with linear branching patterns in the left lung segments S9 and S10, consistent with a tree-in-bud pattern. Diagnostic thoracoscopic wedge resection of the left S9 was performed to exclude inflammatory disease, confirming metastatic colonic adenocarcinoma. Subsequently, 1 month later, left S10 segmentectomy was conducted. Histopathological examination revealed mucus filling the bronchioles in the affected area. This finding indicates that pulmonary metastases from colonic mucinous adenocarcinomas may present as a tree-in-bud pattern. CT findings of this pattern in patients with a history of colon cancer with extracellular mucus require thorough evaluation.

•The tree-in-bud pattern is a common chest CT finding.•The tree-in-bud pattern is typically associated with inflammation.•The tree-in-bud pattern is atypical for metastases from colon cancer.•Extracellular mucus from mucinous adenocarcinoma caused this tree-in-bud pattern.

The tree-in-bud pattern is a common chest CT finding.

The tree-in-bud pattern is typically associated with inflammation.

The tree-in-bud pattern is atypical for metastases from colon cancer.

Extracellular mucus from mucinous adenocarcinoma caused this tree-in-bud pattern.