Halo sign: differential in a gastrointestinal oncology patient
Follow-up for history of rectal adenocarcinoma post abdominoperineal resection. History of adjuvant chemotherapy (unknown agents, duration, or end of last cycle). Asymptomatic.
CT chest, abdomen, and pelvis
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There is a 6 mm nodule in the left lower lobe, with faint surrounding ground glass attenuation, which is new compared with a CT chest from 5 months prior.
3 case question available
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.................?
- 1. Ginsberg MS, Griff SK, Go BD et-al. Pulmonary nodules resected at video-assisted thoracoscopic surgery: etiology in 426 patients. Radiology. 1999;213 (1): 277-82. doi:10.1148/radiology.213.1.r99oc08277 - Pubmed citation
- 2. Seo JB, Im JG, Goo JM et-al. Atypical pulmonary metastases: spectrum of radiologic findings. Radiographics. 2001;21 (2): 403-17. doi:10.1148/radiographics.21.2.g01mr17403 - Pubmed citation
- 3. Gaeta M, Volta S, Scribano E et-al. Air-space pattern in lung metastasis from adenocarcinoma of the GI tract. J Comput Assist Tomogr. 1996;20 (2): 300-4. Pubmed citation