# Micro‐Computed Tomography Based Whole Block Imaging of Asthma‐Associated Airway Remodeling With Mycobacterium avium‐Induced Cavity Formation: 3‐Dimensional Nondestructive Analysis

## TL;DR

This study uses 3D imaging to show how asthma-related airway changes may help spread Mycobacterium avium infections in the lungs.

## Contribution

First 3D visualization of a continuous airway route from the hilum to a subpleural cavity in M. avium infection.

## Key findings

- Merged whole block imaging revealed a remodeled airway connecting the hilum to a subpleural cavity with granulomas.
- The airway intertwined with granulomatous tissue, suggesting a structural pathway for mycobacterial spread.
- WBI also showed minor granulomas and calcifications, providing detailed anatomical insights.

## Abstract

Asthma is a recognized risk factor for nontuberculous mycobacterial (NTM) pulmonary infections, yet the precise routes of infection and dissemination remain visually unclear. We analyzed a rare surgical case of asthma complicated by Mycobacterium avium–associated lung cavity formation in a young adult. Following antibiotic treatment, the patient underwent left upper segmentectomy, with successful subsequent treatment of residual lesions using amikacin liposome inhalation suspension. To precisely visualize the infection route, we utilized a three‐dimensional merged whole block imaging (WBI) technique. Fifteen formalin‐fixed paraffin‐embedded tissue blocks from the resected lung were individually scanned using a custom‐built micro‐computed tomography system, reconstructed, and combined to generate merged‐WBI. Three core merged‐WBIs revealed that the remodeled asthma‐associated airway ascended from the proximal hilar region, intertwined with surrounding epithelioid granulomatous tissue, and then descended into a subpleural cavity composed of epithelioid granulomas with central caseous necrosis containing acid‐fast bacilli. Besides the distinct airway path, the WBI delineated the distribution of minor epithelioid granulomas and calcifications. This report provides the first three‐dimensional visualization of a continuous airway route extending from the hilum to a subpleural cavity using merged‐WBI, suggesting bronchial spread as a probable mechanism of NTM dissemination in the setting of chronic airway disease.

Clinical trial registration: No clinical trials.

Subpleural cavities are characteristic of Mycobacterium avium infections, but the precise route of infection remains unclear. Using merged micro‐computed tomography of multiple formalin‐fixed paraffin‐embedded (FFPE) blocks (merged whole block imaging), we visualized a continuous airway path from the hilum to a subpleural cavity. Asthma‐associated bronchial remodeling facilitated airway extension into granulomatous tissue, suggesting a structural mechanism for mycobacterial trapping and airborne spread.