Clustered micronodules as predominant manifestation on CT: A sign of active but indolently evolving pulmonary tuberculosis

Abstract

To investigate the prevalence, patient characteristics, and natural history of clustered micronodules (CMs) in active pulmonary tuberculosis. Materials and methods From January 2013 through July 2018, 833 consecutive patients with bacteriologically or polymerase chain reaction-proven active pulmonary tuberculosis were retrospectively evaluated. CMs were defined as a localized aggregation of multiple dense discrete micronodules, which primarily distributed around small airways distal to the level of the segmental bronchus: small airways surrounded by CMs maintained luminal patency and the CMs might coalesce into a larger nodule. The patients were dichotomized according to whether the predominant computed tomography (CT) abnormalities were CMs. We analyzed radiologic and pathologic findings in patients whose predominant diagnostic CT abnormalities were CMs, along with those of incidental pre-diagnostic CT scans, if available. Chi-square, McNemar, Student t-test and Wilcoxon-signed rank test were performed. Results CMs were the predominant CT abnormality in 2.6% of the patients (22/833, 95% CI, 1.8-4.0%) with less sputum smear-positivity (4.8% vs 31.0%; p = .010) and a similar proportion of immunocompromised status (40.9% vs 46.0%; p = .637) than those without having CMs as the predominant CT abnormality. The time interval for minimal radiologic progression was 6.4 months. The extent of CMs increased with disease progression, frequently accompanied by consolidation and small airway wall thickening. Pathologically, smaller CMs were non-caseating granulomas confined to the peribronchiolar interstitium, whereas larger CMs were caseating granulomas involving lung parenchyma. Two of the five patients with a prediagnostic CT scan obtained more than 50 months pre-diagnosis showed an incipient stage of CMs, in which they were small peribronchiolar nodules.

Active pulmonary tuberculosis: something old, something new, something borrowed, something blue

“…7 ). Furthermore, lung biopsies in patients with early stage TB showing clusters of micronodules on CT and whose acid-fast bacilli (AFB) smear test and PCR assay were negative, demonstrated peribronchiolar granulomas [ 26 ]. Some granulomas were confined to the peribronchiolar interstitium with no caseation necrosis or invasion of the airway or alveolar space.…”

“…Both GS and CS seem to be post-primary in immunocompetent individuals and were described as associated with perilymphatic-predominant nodularity rather than centrilobular-predominant nodularity [ 13 ]. A recent study showed the time interval for minimal radiologic progression of these lesions was greater than 6 months and their extent increased with disease progression, frequently accompanied by a pattern of bronchogenic spread and consolidation [ 26 ].…”

“…Several studies and case reports have demonstrated that GS and CS were correlated with smear negative results [ 26 , 40 , 46 – 48 ]. Clusters of nodules was found to be a positive predictor of initially smear-negative active PTB [ 40 ].…”

“…Clusters of nodules was found to be a positive predictor of initially smear-negative active PTB [ 40 ]. Cases with clusters of micronodules as the predominant CT abnormality show significantly less sputum smear positivity than those without this CT predominant pattern [ 26 ]. Moreover, in a subgroup analysis which solely included subjects without cavity, AFB smear positivity was significantly lower in the clusters of micronodules-predominant cases.…”

Correlation Between CT Features of Active Tuberculosis and Residual Metabolic Activity on End-of-Treatment FDG PET/CT in Patients Treated for Pulmonary Tuberculosis

“…Computed tomography (CT) is a more widely available imaging tool in TB-endemic regions of the world. Certain features on CT, including lung consolidation, lung nodules in the typical tree-in-bud pattern, pleural effusion, and others, are known to suggest active PTB ( 14 – 16 ). Determining the strength of the association between these CT features suggestive of active TB and the RMA on FDG PET is crucial for guiding the application of CT, a more widely available imaging technique, for treatment response assessment of patients treated for PTB.…”