Study Syllabus for Classification of Radiographs of Pneumoconioses
Pathology Basis of Occupational Lung Disease
Coal Workers’ Pneumoconiosis
CWP is defined as parenchymal lung disease secondary to the inhalation of coal mine dust, which includes both carbonaceous (coal) and noncarbonaceous minerals such as silica and silicates. The composition of coal mine dust and the severity of exposure varies with the miner’s job description [“Pathology standards,” 1979; Green and Vallyathan 1998]. Like silicosis, CWP is classified as simple or complicated depending on the size of individual lesions.
Inhaled coal particles within the lung are coarse, irregular, often angulated, and black (Fig. 23). The earliest and most distinctive lesion of simple CWP is the coal macule. On macroscopic examination coal macules appear as barely palpable (or nonpalpable) darkly pigmented foci, ranging in size from approximately 1 to 5 mm (Fig. 24). Microscopically, macules are formed by the deposition of black pigment, with minimal associated fibrosis within and around the walls of respiratory bronchioles and alveolar ducts. Airspace dilatation around the macule, termed focal emphysema, is an integral component of the lesion and is considered to represent a form of centrilobular emphysema (Fig. 25) [“Pathology standards,” 1979; Green and Vallyathan 1998]. Simple CWP may also include the presence of small, heavily pigmented, fibrotic nodular lesions of 2 morphological forms: stellate lesions of mixed-dust fibrosis (Fig. 21) or rounded nodules resembling silicotic nodules (Fig. 26). The formation of fibrotic nodules is thought to be related to the content of silica in inhaled coal mine dust [Green and Vallyathan 1998].