Radiological features associated with granuloma positivity on transbronchial lung biopsy in Mycobacterium avium complex pulmonary disease

Abstract Background Although microbiological confirmation remains fundamental for the diagnosis of Mycobacterium avium complex pulmonary disease (MAC-PD), transbronchial lung biopsy (TBLB) may provide supportive histopathological information and help exclude alternative diagnoses in selected patients. However, the influence of radiological features on granuloma detection in TBLB remains unclear. This study aimed to investigate the association between radiological features and granuloma positivity in TBLB specimens. Methods This single-center retrospective study included 69 patients with microbiologically confirmed MAC-PD who underwent TBLB. Radiological forms were classified as non-cavitary nodular-bronchiectatic (NC-NB), cavitary nodular-bronchiectatic (C-NB), and fibrocavitary (FC). Maximum lesion diameter of the biopsy target was measured on chest computed tomography. Univariable and multivariable logistic regression analyses were used to identify factors associated with granuloma positivity. Receiver operating characteristic (ROC) analysis was performed to determine the optimal lesion-size cutoff. Results Granuloma positivity differed significantly among radiological forms, occurring in 15.9% (7/44) of NC-NB, 50.0% (7/14) of C-NB, and 81.8% (9/11) of FC cases ( p < 0.001). ROC analysis identified 20 mm as the optimal cutoff for predicting granuloma positivity (area under the curve = 0.81). Multivariable analysis demonstrated that C-NB (odds ratio [OR] 4.86; 95% confidence interval [CI] 1.17–21.32), FC (OR 8.73; 95% CI 1.27–59.92), and lesion diameter ≥ 20 mm (OR 7.05; 95% CI 1.69–29.48) were independently associated with granuloma positivity. Conclusions Cavitary radiological forms (C-NB and FC) and a maximum lesion diameter ≥ 20 mm were independently associated with granuloma positivity on TBLB in patients with MAC-PD.