Halo sign: differential in a gastrointestinal oncology patient
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
- renal cell carcinoma
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
- 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.................?