Study Syllabus for Classification of Radiographs of Pneumoconioses


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Pathology Overview

Pathology Basis of Occupational Lung Disease

Pathologic–Radiological Correlations

Silica and Coal Dust

Although the chest radiograph is an excellent method for assessing the degree of involvement of the lung in CWP and silicosis, certain limitations are recognized. Individual lesions less than 3 mm in maximal dimension usually cannot be visualized radiographically. Therefore, in early macular CWP or nodular silicosis the chest radiograph may appear as “normal.” Radiologic summation effect due to the superimposition of numerous small nodules may nonetheless result in the appearance of small round opacities.5 The ILO system serves as a means of classifying chest radiographs of individuals with pneumoconiosis. It does not define pathologic entities. The distinction between CWP and silicosis by chest radiography alone is usually not possible. Nodular lesions of simple CWP and simple silicosis appear as rounded opacities measuring up to 1 cm in diameter on a chest radiograph.5 Small irregular opacities are less frequent. Lesions of complicated pneumoconiosis are represented radiographically by large opacities that exceed 10 mm in the longest dimension.

Studies correlating lung pathology with ILO Classification in CWP have shown that small p-type opacities correlate with dust macules and emphysema (Fig. 24), (Fig. 25). Larger q- and r-type opacities are seen as fibrotic nodular lesions.6,33-34 Type q opacities have been associated with nodular lesions measuring from 1 to 7 mm, while r-type opacities correlate with macronodules measuring from 7 to 10 mm.33 Ruckley et al correlated stellate nodules (Fig. 21) with q-type opacities and round silicotic-type nodules with r-type opacities34 (Fig. 26). There is also a positive correlation between mean weight of retained lung dust and radiographic profusion score for small round opacities in CWP.34 Small irregular opacities in coal workers are somewhat less frequent than rounded opacities and have been associated with emphysema and/or pigment-laden interstitial fibrosis.34-35 (Fig. 31)

In patients with rapidly progressive pneumoconiosis, features of silicosis were significantly associated with rounded (p, q, r) opacities on chest imaging, while high-grade interstitial fibrosis was associated with the presence of irregular (s, t, u) opacities.8

Page last reviewed: March 11, 2019