Pericardial fat necrosis mimicking pyothorax.

A 34-year-old man was referred to our institution for treatment of pyothorax that had proven to be incurable with antibiotics. His symptom was acute left chest pain. Abnormal findings were absent in the laboratory data and an electrocardiogram. A chest radiograph showed a left pericardial shadow and pleural effusion (Picture A). Chest CT revealed a mass adjacent to the thickened pericardium with low attenuation values equivalent to subcutaneous fat (Picture B, C). Based on the clinical and radiologic findings, a diagnosis of pericardial fat necrosis was tentatively made. The patient was observed with analgesics, and his pain gradually disappeared within ten days. One month later, chest CT showed a reduced mass without contrast enhancement, while the pleural effusion and pericardial thickening had vanished (Picture D). Pericardial fat necrosis is a benign and noninfectious disease with an unknown cause that can be diagnosed based on the presence of unique CT features. The management does not require any intervention, including antibiotics or surgery (1).