The so-called galaxy sign, initially described as the sarcoid galaxy, represents a coalescent granuloma seen in a minority of patients with pulmonary sarcoidosis 1. The same appearance can be seen in tuberculosis 2,3. In other words, it represents a mass-like region composed of numerous smaller granulomas. The appearance of a central core with peripheral nodules is reminiscent of a globular cluster galaxy.
Central cavitation does occur and the lesions may be surrounded by ground-glass opacity. The latter is thought to represent extensive interstitial sarcoid granulomas below the resolution of HRCT rather than alveolitis or haemorrhage 1.
- 1. Nakatsu M, Hatabu H, Morikawa K et-al. Large coalescent parenchymal nodules in pulmonary sarcoidosis: "sarcoid galaxy" sign. AJR Am J Roentgenol. 2002;178 (6): 1389-93. AJR Am J Roentgenol (full text) [pubmed citation]
- 2. Heo JN, Choi YW, Jeon SC et-al. Pulmonary tuberculosis: another disease showing clusters of small nodules. AJR Am J Roentgenol. 2005;184 (2): 639-42. AJR Am J Roentgenol (full text) [pubmed citation]
- 3. Aikins A, Kanne JP, Chung JH. Galaxy sign. J Thorac Imaging. 2012;27 (6): W164. doi:10.1097/RTI.0b013e31826b7e6f - Pubmed citation
- systemic manifestations
- pulmonary and mediastinal manifestations (chest x-ray staging)
- cardiac manifestations
- musculoskeletal manifestations
- head and neck manifestations
- central nervous system manifestations
- abdominal manifestations
- cutaneous manifestations