Transformation of a pericardial cyst observed on long-term follow-up

An atypical pattern of pericardial cyst was observed on a routine chest radiograph of a healthy 25-year-old woman. It appeared as an important elevation of the right diaphragm. The cystic nature of the mass was easily disclosed by ultrasonography and computed tomography, but its location--thoracic, diaphragmatic, or subphrenic--remained questionable. Finally, a percutaneous puncture yielded 1300 mL of clear liquid. Despite this huge volume, the cyst had been asymptomatic and did not recur after complete aspiration. Retrospectively, owing to previous files, we could recognize the evolution of a pericardial cyst from the age of 13 years. At that time, it was much smaller and was evaluated by a series of aggressive investigations, although it had a more typical pattern and was confined to the right cardiophrenic angle.