Multiple huge "cluster" and "galaxy" signs on chest radiography in a patient with pulmonary tuberculosis

A 62-year-old healthy man presented to our hospital due to a persistent fever of up to 38°C for one week. Thoracic computed tomography showed right pleural effusion with multiple large nodules up to 7 cm in diameter composed of numerous discrete small nodules like fireworks, the so-called "cluster" signs. Some of the large nodules had a hyper-dense portion centrally surrounded by partially discrete small nodules, not as densely assembled, suggestive of the "galaxy" sign. The repeated acid-fast sputum smears and both bronchial washings were all negative for Mycobacterium tuberculosis, but the acid-fast culture of sputum taken soon after the first bronchoscopy, and pleural fluid, turned out to be positive for M. tuberculosis at six weeks after admission. The present case clearly demonstrates that the "galaxy" and "cluster" signs are red herring signs of the low rates of isolating M. tuberculosis, which should be differentiated from pulmonary sarcoidosis.