Correct!
4. Observation only
The imaging features are consistent with a particular diagnosis, and invasion testing is not necessary. Therefore, percutaneous transthoracic fine needle aspiration biopsy and mediastinoscopy are not the correct answers. The risk of spillage of the cystic content during percutaneous transthoracic fine needle aspiration biopsy is unacceptably high whereas the likelihood of obtaining a histopathological diagnosis is low for this cystic, isolated, indolent-appearing, and incidentally detected lesion. The lesion is too caudal in the subcarinal space to be reached via mediastinoscopy. While 18FDG-PET could potentially be a useful procedure for the evaluation of mediastinal lesions, as it has the ability to assess for metabolic activity within the lesion as well as the ability to detect potential sites of disease elsewhere within and outside the thorax, the lesion has already been well-characterized by cross sectional imaging. The lack of tracer utilization within the lesion would simply reinforce the impression of a benign abnormality, whereas increased tracer utilization would most likely prompt incorrect consideration of an aggressive process for this lesion. 68Ga-citrate scintigraphy would not provide addition useful information in this patient.
Based on the data thus far, which of the following represents the most likely diagnosis for this patient? (Click on the correct answer to proceed to the seventh and final panel)