Clinical/pathologic correlations in 553 patients with primary centrilobular findings on high-resolution CT scan of the thorax.

Background: Clinical/pathologic correlations in patients with high-resolution CT (HRCT) scan findings presenting with two patterns of centrilobular opacity remain unclear.
Methods: Chest HRCT scans in 553 patients with predominant centrilobular opacities or preferential centrilobular disease were retrospectively evaluated. In 141 patients who underwent biopsy, CT scan images were compared with actual specimens.
Results: Centrilobular nodules with a tree-in-bud appearance and bronchial wall thickening were observed in most patients who were carriers of human T-lymphotropic virus type 1 (88 patients and 57 of 99 patients, respectively), Mycoplasma pneumoniae pneumonia (44 patients and 45 of 52 patients, respectively), Mycobacterium tuberculosis (38 patients and 37 of 52 patients, respectively), Mycobacterium avium-intracellulare complex (22 patients and 27 of 37 patients, respectively), Mycobacterium kansasii (27 patients and 19 of 33 patients, respectively), allergic bronchopulmonary aspergillosis (6 patients and 7 of 9 patients, respectively), diffuse panbronchiolitis (12 patients and 10 of 12 patients, respectively), and diffuse aspiration bronchiolitis (12 patients and 12 of 13 patients, respectively). On the other hand, ill-defined centrilobular nodules of ground-glass attenuation were frequently seen in patients with subacute hypersensitivity pneumonitis (all 15 patients), metastatic calcification (all 4 patients), Churg-Strauss syndrome (4 of 12 patients), microscopic polyangiitis (27 of 48 patients), systemic lupus erythematosus (7 of 8 patients), and respiratory bronchiolitis-associated interstitial lung disease (all 8 patients). Pathologically, the tree-in-bud appearance correlated well with the plugging of small airways with mucous, pus, or fluid; dilated bronchioles; and bronchiolar wall thickening. Ill-defined centrilobular nodules represented peribronchiolar inflammation or the deposition of hemorrhagic materials.
Conclusions: Knowledge of the two centrilobular patterns is of proven worth for generating differential diagnoses and is of particular value in suggesting a likely infectious etiology in cases with tree-in-bud appearance.