Halo sign: differential in a gastrointestinal oncology patient

Discussion:

The ground glass halo around a nodule suggests involvement of the adjacent alveoli or septa at a resolution too fine for our CT equipment... it could represent either fluid/hemorrhage or possible "lepidic" growth of a tumor (as with bronchoalveolar cell carcinoma).

A pulmonary metastasis may be surrounded by a peritumoral hemorrhage and result in a ground glass nodule. Certain metastases do this more commonly, such as 2

  • melanoma
  • renal cell carcinoma
  • choriocarcinoma
  • angiosarcoma

However, the ground glass nodule is not a specific finding, and in the setting of an oncologic patient, who may be immunocompromised from chemotherapy, it is prudent to suggest a differential that includes infectious processes that have ground glass halos, such as 2

  • angioinvasive aspergillosis
  • candidiasis
  • possibly, tuberculoma

Lymphoma and a lymphoproliferative process may also present with ground glass nodules/masses... another consideration an immunocompromised patient.

Gastrointestinal adenocarcinoma mets have been shown to have a lepidic pattern of growth. They may uncommonly present with a ground glass halo (~3%). 3

So should one call this new nodule with a ground glass halo a metastasis or an infectious nodule?

It realistically could be either. If all infectious nodules have a ground glass halo, then a metastasis would have to be 30x more likely than infection for this to be an even split.................?

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