Aetiologic diagnosis of thoracic granulomatous diseases: a retrospective multicentre study in South-Central China

Objectives To characterise the aetiological spectrum of thoracic granulomatous diseases and identify diagnostic features that facilitate differentiation among causes. Design Retrospective multicentre observational study. Setting Two tertiary hospitals in south-central China. Patient data were consecutively enrolled from 1 June 2020 to 30 June 2023. Participants Of 2486 patients with pathologically confirmed thoracic granulomas initially identified, exclusions were applied for specimens outside the lung/pleura/mediastinum (579), incomplete demographic/imaging/pathology data (280) or lack of follow-up (231). A total of 1396 patients met all criteria (853 from hospital 1 and 543 from hospital 2) and were included in the final analysis. Primary and secondary outcome measures We quantified the aetiologic distribution of thoracic granulomatous diseases and examined age-stratified/lesion-location differences in aetiologic patterns. We also evaluated associations between histopathological features and specific aetiologies and compared the diagnostic accuracy across sampling modalities. Results Among the 1396 enrolled cases, a confident, probable and uncertain diagnosis was made in 1086 cases, 307 cases and 84 cases. Infectious granulomas predominated (89.4%; 1248/1396), with tuberculosis comprising 87.8% (1096/1248) of infectious cases. Among non-infectious granulomas, sarcoidosis was most common (65.8%; 50/76). Patients aged ≥60 years had a higher proportion of infectious granulomas than younger groups (≥60 years: 389/422; 40-60 years: 633/714; Conclusions Most thoracic granulomas arise from mycobacterial or fungal infection, while sarcoidosis is the leading non-infectious cause. Thoracoscopy and surgical biopsy show superior diagnostic yields, and special staining aids differentiation of fungal aetiologies. Findings support a multidisciplinary approach to improve diagnostic accuracy.