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.

CoVID-19 Imaging Appearance

We have collected several cases from our institution of proven CoVID-19 disease. The majority of these display typical imaging manifestations: on chest radiograph, either diffuse interstitial opacities or peripheral airspace opacities; on CT, peripheral predominant ground glass or consolidative opacities.

Chest Radiograph

40-year-old man with peripheral-predominant airspace disease

84-year-old woman. Note peripheral predominance in the right lung.

60-year-old woman with diffuse interstitial opacities

60-year-old man with diffuse interstitial opacities

59-year-old man

Chest CT – Typical

78-year-old woman

Note peripheral opacity with reverse halo sign
And other more nodular opacity

31-year-old man

Peripheral patchy ground glass opacities

Chest CT – Atypical

83-year-old woman

Note diffuse ground glass with some septal thickening

80-year-old female

Small subpleural nodular opacity, unclear if related to CoVID-19
Minimal septal thickening and pleural effusions, likely related to edema.