Astronomy: Galaxy Sign and Black Hole Sign

Galaxy Sign

The galaxy sign represents coalescing granulomatous inflammation in sarcoidosis. Large nodules with surrounding micronodules are characteristic – even pathognomonic – of sarcoidosis.

Two patients with sarcoidosis demonstrating the galaxy sign:

“Large Coalescent Parenchymal Nodules in Pulmonary Sarcoidosis: “Sarcoid Galaxy” Sign.” Am J Roentgenol 2002.

Black Hole Sign

Patients with angioinvasive fungal pneumonia caused by Mucormycosis develop necrotizing infarction of the lung parenchyma. This portion of the parenchyma will be completely non-enhancing at MRI and appear as a ‘black hole.’

Black hole sign in the right upper lobe

“Pulmonary Mucormycosis: Radiologic Features at Presentation and Over Time” Am J Roentgenol 2018.

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