# Mesenchymal‐epithelial transition factor exon 14 skipping mutation‐positive granulocyte colony‐stimulating factor‐producing lung adenocarcinoma mimicking lung abscess: A case report

## TL;DR

A rare case of lung cancer with a specific genetic mutation mimicked a lung abscess and responded to targeted therapy.

## Contribution

Reports a rare case linking MET exon 14 skipping mutation and G-CSF-producing lung cancer mimicking abscess.

## Key findings

- The patient's tumor responded to tepotinib therapy, reducing both the lesion and G-CSF levels.
- G-CSF-producing lung tumors can have imaging features similar to lung abscesses.
- MET exon 14 skipping mutations are uncommon but clinically significant in lung adenocarcinoma.

## Abstract

Granulocyte colony‐stimulating factor (G‐CSF)‐producing lung tumours are rare, with their imaging features and effective treatments remaining elusive. Similarly, mesenchymal‐epithelial transition (MET) exon 14 skipping mutations are also uncommon. Herein, we report a case of G‐CSF‐producing lung adenocarcinoma positive for a MET exon 14 skipping mutation, mimicking lung abscess. A 61‐year‐old man presented with cough and high fever. Contrast‐enhanced chest computed tomography revealed a mass with a cavity and internal fluid accumulation. The patient initially underwent diagnostic treatment for a lung abscess but was ultimately diagnosed with lung adenocarcinoma positive for a MET exon 14 skipping mutation. Following tepotinib therapy, the primary lesion shrank, and serum G‐CSF levels decreased, leading to a diagnosis of G‐CSF‐producing lung cancer. G‐CSF‐producing lung tumours can present imaging findings that mimic lung abscesses. Tepotinib therapy may be effective for patients with MET exon 14 skipping mutation, including those with G‐CSF‐producing lung cancer.

Granulocyte colony‐stimulating factor (G‐CSF)‐producing lung tumours are rare, with their imaging features and effective treatments remaining elusive. Similarly, mesenchymal‐epithelial transition (MET) exon 14 skipping mutations are also uncommon. Herein, we report a case of G‐CSF‐producing lung adenocarcinoma positive for a MET exon 14 skipping mutation, mimicking lung abscess.