Pulmonary malignancy in silicosis: factors associated with radiographic detection

The aim was to assess radiographic features of pulmonary malignancies in silicosis and to reveal confounding factors in their detection. A total of 501 silicosis patients were followed up between 1982 and 2003. Sixty pulmonary malignancies were pathologically confirmed in 54 (10.8%) patients. Two radiologists reviewed serial radiographs of these patients to determine radiographic features of tumor (size, margin, nodule or consolidation, localization, overlying structures) and silicosis (profusion of pneumoconiotic opacities, progressive massive fibrosis (PMF), hilar lymphadenopathy). Eleven tumors were radiographically negative. Forty-nine tumors were retrospectively visible with radiograph. Of these, 15 tumors were clinically detected with radiograph, but 25 were missed. The remaining nine tumors became radiographically positive after positive sputum cytology. There were no differences between missed and detected nodules in terms of radiographic findings. The mean tumor size was 30mm (range: 15-90mm) and was significantly larger in patients with PMF or hilar lymphadenopathy than in those without (35mm vs. 24mm, p=0.006; 33mm vs. 24mm, p=0.038, respectively). This was correlated with background profusion of small pneumoconiotic opacities (r=0.433, p=0.024). Retrospective reading tests by three radiologists showed correct localization of tumor in 75%, however, the correct diagnosis with a high confidence was reached in only 54%. In conclusion, radiographic detection of malignancy in silicosis proved a difficult task and no single radiographic finding was found to be associated with missing the tumor. The presence of PMF, hilar lymphadenopathy and profusion of small pneumoconiotic nodules affected tumor size at detection.