Pleural pseudotumors refer to encysted focal pleural fluid collections located within a lung fissure, and often appear as lenticular or biconvex shaped opacities on plain radiographs. This radiograph was performed as part of a septic screen in the context of neutropenic fever and recent fluid overload.

A CT pulmonary angiogram performed two weeks prior demonstrated a large right pleural effusion, small left pleural effusion, large pericardial effusion, and bilateral patchy centrilobular consolidation: appearances consistent with fluid overload, but potentially also explained by pericarditis or atypical pulmonary infection.

A chest x-ray performed two weeks prior demonstrated a large right sided pleural effusion but no evidence of encysted pleural fluid.

In this context, the above findings were thought to most likely represent a pleural pseudotumor due to the recent history of fluid overload. Differential diagnoses included pleural infection or pleural-based mass. The acute nature of its appearance (within two weeks) makes malignancy less likely.