Subcostal loculated pleural effusion in congestive heart failure: an unusual case of vanishing tumor.

Localized collection of fluid in an interlobar fissure as a consequence of congestive heart failure is a well-known entity. It has been termed vanishing tumor because of its appearance as a mass lesion in the lung and its propensity to resolve with diuretic therapy. We report a case of loculated pleural effusion in the subcostal pleural space without interlobar fluid collection. This was initially thought to represent an occult metastatic malignancy; however, the cause of the density became obvious when it disappeared with therapy of heart failure and recurred concurrent with cardiac decompensation. Loculated pleural effusion must be included in the differential diagnosis of roentgenographic densities in the chest when seen in subcostal as well as in interlobar locations.