Pulmonary tuberculosis presenting multiple nodular shadows in 4 patients

: Four cases of multiple nodular pulmonary tuberculosis simulating metastatic lung cancer were reported. These patients were asymptomatic, found by chance during physical checkups, and had no clinical findings indicative of inflammatory reactions. The nodules ranged from 15 to 50 in number, were spherical in shape, and 3-10 mm in diameter with sharp margins. In 2 patients, the size of the Mantoux reaction (using purified protein derivative) was 22 mm and 11 mm respectively; the other 2 patients were not given the skin test. The final diagnosis was made by video-assisted thoracoscopic surgery in 2 patients, percutaneous lung biopsy in 1, and open lung biopsy in 1. Epithelioid cell granulomas were found in all 4. Anti-tuberculous chemotherapy reduced the size of the nodules significantly in 2 patients and slightly in 1. One patient did not undergo chemotherapy. Although no acid-fast bacilli were detected, all 4 patients were given a diagnosis of pulmonary tuberculosis on the basis of the above findings. Whenever multiple nodular shadows are observed, it is common to suspect metastatic lung cancer at the outset. However, our experience indicated that pulmonary tuberculosis also should be kept in mind as a candidate for differential diagnosis. Computed tomographic findings suggested that the lesions were caused by hematogenous dissemination. Our report therefore devoted some attention to mechanisms of formation.