Fig. 18.7 Follicular bronchiolitis in a 61-year-old man with Sjögren’s syndrome. (a, b) Lung window images of thin-section CT scans (1.5- mm section thickness) obtained at levels of aortic arch (a) and right inferior pulmonary vein (b), respectively, show small centrilobular nodules and branching nodular structures (tree-in-bud signs, arrows) in superior and posterior basal segments of right lower lobe. (c) Low-

magnification (×40) photomicrograph of surgical biopsy specimen obtained from right lower lobe demonstrates bronchiolocentric (Br) inflammatory lesions (arrows). (d) High-magnification (×200) photomicrograph discloses narrowed or obliterated bronchiolar lumen (Br) owing to dense lymphocyte infiltrates (arrows). Ao arteriole

symptoms, such as fatigue, weight loss, night sweating, and fever, are not uncommon. Some patients may be asymptomatic.

CT Findings

The most common TSCT findings of nodular bronchiectatic form of NTM pulmonary disease include centrilobular small nodules or tree-in-bud pattern, with tubular bronchiectasis, usually in right middle lobe, the lingular segment of left upper lobe, and both the lower lobes [8, 9] (Fig. 18.5). TSCT findings of bronchiectasis and bronchiolitis involving more than five lobes, especially when associated with lobular consolidation or a cavity, are highly suggestive of NTM pulmonary disease [9].

CT–Pathology Comparisons

Centrilobular small nodules, tree-in-bud pattern, and bronchiectasis correspond histopathologically to bronchiectasis and bronchiolar and peribronchiolar inflammation with or without granuloma formation [8]. NTM pulmonary disease is mainly a bronchocentric or bronchiolocentric inflammatory process [23]. It begins with bronchial or bronchiolar wall thickening and develops into peribronchial or peribronchiolar thickening or a peribronchial nodule. Nodular bronchiectatic form of NTM disease on TSCT represents this stage of inflammation mainly involving small airways. During the inflammatory process, the central necrotic portion with destroyed bronchial wall and cartilage seems to be ulcerated and detached into the airway. In this circumstance, the central patent bronchus disposes of the detached central necrotic