Halo sign

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[edit] Discussion of Halo sign

  • The halo sign refers to a zone of ground-glass attenuation surrounding a pulmonary nodule or mass on CT images.
  • The presence of a halo of ground-glass attenuation is usually associated with hemorrhagic nodules.
  • In severely neutropenic patients, the halo sign is highly suggestive of infection by an angioinvasive fungus, most commonly Aspergillus.
  • Vascular invasion by this fungus results in thrombosis of small- to medium-sized vessels, which causes ischemic necrosis.
  • At pathologic examination, the nodules represent foci of infarction, and the halo of ground-glass attenuation results from alveolar hemorrhage.
  • Although it is less common, the halo sign may also be observed in nonhemorrhagic nodules, in which case either tumor cells or inflammatory infiltrate account for the halo of ground-glass attenuation.

[edit] Images

Patient #1

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[edit] References for Halo sign