# Rare Case of Focal Organising Pneumonia With Extension to Interlobar Space and Adjacent Lobe Initially Suspected as Lung Cancer

## TL;DR

A rare case of focal organizing pneumonia was mistaken for lung cancer due to its unusual extension into the interlobar space and adjacent lobe.

## Contribution

This is the first reported case of focal organizing pneumonia extending to the interlobar space and adjacent lobe.

## Key findings

- Focal organizing pneumonia was initially suspected as lung cancer due to its appearance on imaging.
- The case extended to the interlobar space and adjacent lobe, a previously unreported feature.
- The condition may have been caused by Fusobacterium nucleatum infection.

## Abstract

Organising pneumonia is histopathologically characterised by inflammatory granulation tissue plugs within the lumen of the small airways, extending into the alveolar ducts and airways. Focal organising pneumonia is an organising pneumonia that presents as a solitary nodule or mass on computed tomography. This type of organising pneumonia is sometimes initially suspected to be lung cancer. We report a rare case of focal organising pneumonia that extended to the interlobar space and adjacent lobe and was initially suspected of lung cancer with interlobar pleural invasion. This case of focal organising pneumonia may have been induced by
Fusobacterium nucleatum
infection. This is the first report of a focal organising pneumonia extending to the interlobar space and adjacent lobe.

We report a rare case of focal organising pneumonia (FOP) that was initially suspected to be lung cancer with interlobar pleural invasion and extension to the interlobar space and the adjacent lobe.