The illustrated chest x-ray and computed tomographic scan of a 25 year old man with progressive shortness of breath are consistent with 

A. extralobar sequestration. 
B. hernia through the foramen of Bochdalek. 
C. hernia through the foramen of Morgagni. 
D. large pericardial effusion. 
E. pericardial cyst.

Answer C

The images display a mass of fat density in the right chest and anterior abdomen. The pericardial edge is visible which makes this inconsistent with a large pericardial effusion. While a pericardial cyst can occur in a lower thoracic location, its density is not usually that of fat; it is typically smaller and more round. The triangular central upper abdominal component of this lesion suggests that the fat may be in communication with the abdominal fat. A foramen of Morgagni hernia occurs anteriorly through a triangular space between the muscular fibers of the diaphragm and the sternum. The internal mammary artery passes through this space. At this point, a large hernia can develop. The hernia characteristically enlarges with time so that clinical presentation is usually in late adolescence or adulthood. Obese patients are more affected. Repair is conducted through the abdomen anteriorly. 

A foramen of Bochdalek hernia is located posteriorly and laterally in the central portion of the diaphragm. Sequestrations are characteristically located posteriorly in the chest and do not generally exhibit a fat density or the peculiar triangular diaphragmatic abnormality anteriorly that is illustrated.