Study Syllabus for Classification of Radiographs of Pneumoconioses
Subset 4 – Small and Large Opacities
Cancer of the lung is the most common lethal cancer. Lung cancer survival is related to the stage at diagnosis, with much better prognosis for those diagnosed at earlier stages. Thus it is important to identify findings suspicious for lung cancer in chest radiographs and ensure that there is appropriate, timely notification of results so that patients can receive timely follow-up diagnostic and therapeutic care. It is also important to recognize that mineral dusts such as asbestos and crystalline silica don’t only cause pneumoconiosis and have been identified by the International Agency for Research on Cancer as known human lung carcinogens. In addition, some reports have suggested that coal miners may be at increased risk for lung cancer mortality. The radiologic distinction between a large opacity and a malignant neoplasm is extremely difficult; in fact, the two conditions may be reported in the same chest radiograph.
It is often difficult to distinguish between large opacities and malignancy. Things to consider are: 1) A large opacity of pneumoconiosis is almost invariably associated with an unequivocal background of small pneumoconiotic opacities with a profusion level of category 1/0 or greater. As large opacities increase in size, however, they may appear to incorporate surrounding small opacities. Moreover, as they enlarge, emphysematous changes in the surrounding lung become increasingly apparent. As a result, the profusion of small opacities surrounding a large opacity may appear to diminish over time and in rare cases may disappear entirely. 2) The large opacity of pneumoconiosis will usually have at least one rather sharply defined border, whereas the shadows of malignant neoplasms are often completely ill-defined. The margination of a shadow alone, however, is not a reliable characteristic on which to base the distinction between a benign pneumoconiotic opacity and a malignant neoplasm. 3) Longitudinal evaluation of serial imaging may be helpful. The large opacities of pneumoconiosis may change very slowly, usually over the course of years. Opacities representing carcinomas tend to change more rapidly.
Finally, 4) If large opacities are bilateral and symmetrical one might consider this to be more likely PMF rather than malignancy.
You should by now be familiar with the form for reporting your classification of chest radiographs according to the ILO 2011 system. You have reviewed representations of the radiographic findings characteristic of pneumoconiosis and have been instructed in the conventions to be observed in quantifying them. It remains now for you to apply your knowledge to the interpretation of clinical radiographs. Radiographs #47 through #83 provide you with this opportunity.