Pneumoconiosis

Fig. 18.9 Pulmonary sarcoidosis manifesting perilymphatic nodules in a 31-year-old man. (a, b) Lung window images of thin-section (1.0-mm section thickness) CT scans obtained at levels of aortic arch (a) and right upper lobar bronchus (b), respectively, show small nodules along bronchovascular bundles (arrows), subpleural lungs (open arrows), and

in centrilobular areas (curved arrows). Also note thickening of bronchovascular bundles (small arrows) indicative of perilymphatic lesions of sarcoidosis. (c) Coronal reformatted image (2.0-mm section thickness) demonstrates upper lung zone predominance of perilymphatic nodular lesions

Pneumoconiosis

Pathology and Pathogenesis

Pneumoconiosis is defined as permanent alteration of the lung structure due to the inhalation of mineral dust and the

tissue reactions of the lung to its presence, excluding bronchitis and emphysema. To reach the lung, dust particles have to be very small. Particle density and shape also affect the aerodynamic properties of dust. Host factors such as airflow characteristics, airway branching patterns, and airway disease also affect dust deposition [40].

Fig. 18.10 Pneumoconiotic nodules showing perilymphatic distribution in a 32-year-old building demolition worker. (a, b) Lung window images of thin-section (1.0-mm section thickness) CT scans obtained at levels of right upper lobar bronchus (a) and distal bronchus intermedius (b), respectively, show small nodules along fissures (arrows), subpleural lungs (open arrows), and in centrilobular regions (arrowheads). (c) Low-magnification (×10) photomicrograph of surgical biopsy speci-

men obtained from right upper lobe demonstrates multiple noncaseating and fibrotic granulomas having perilymphatic distribution; granulomas are located along pleura (arrows) and in alveolar walls (arrowheads). (d) High-magnification (×2,000 photomicrograph discloses a well-circumscribed pneumoconiosis nodule (arrows) composed of mature collagen in the central portion, with a peripheral zone of particle-laden macrophages

Symptoms and Signs

Some patients with pneumoconiosis are asymptomatic and diagnosed incidentally after radiographic screening examination. They may have a dry cough. Shortness of breath is more common at later stages, especially with progressive massive fibrosis. Other patients can present with associated conditions such as tuberculosis and lung cancer.

CT Findings

On TSCT, the most characteristic feature of pneumoconiosis is the presence of multiple small nodules of 2–5 mm in diameter (Fig. 18.10). The nodules are seen mainly in the centrilobular regions, reflecting their peribronchiolar localization. They are also seen in the subpleural regions and along the interlobular septa because of their perilymphatic distribution [40]. The nodules tend to involve mainly dorsal regions of

the upper lobes and are most numerous in the right upper lobe [41].

When nodules coalesce to form opacities larger than 10 mm in diameter, they are called progressive massive fibrosis (PMF). PMF tends to develop in the periphery of the upper and middle lung zones and often appears to migrate gradually toward the hila. Foci of emphysema are often present between the conglomerate mass and the pleura. The opacities are usually bilateral and symmetric.

CT–Pathology Comparisons

Inhaled inorganic particles that land on the epithelium of the respiratory bronchioles enter the adjacent interstitium, where they accumulate within macrophages. Particles that land in the alveoli in the periphery of the lung also accumulate within macrophages in the