Unexplained Massive Pericardial Effusion Revealing Intrapericardial Lymphangioma.

BACKGROUND: Intrapericardial lymphangioma is a rare benign lymphatic tumor that may present with nonspecific findings and unexplained pericardial effusion, posing a diagnostic challenge. CASE SUMMARY: A 33-year-old woman presented with dyspnea and a large pericardial effusion without tamponade. Multimodality imaging revealed multiloculated pericardial and mediastinal lesions, but diagnosis remained uncertain. Because of inconclusive findings, surgical biopsy was performed. Histopathology and immunohistochemistry (ETS-related gene, CD31, and D2-40) confirmed intrapericardial lymphangioma. The patient underwent partial pericardiectomy with a favorable outcome. DISCUSSION: Noninvasive modalities may be insufficient to determine the etiology of pericardial effusion with associated masses. Tissue diagnosis is often required. TAKE-HOME MESSAGE: Early tissue diagnosis should be considered in unexplained pericardial effusion when imaging is inconclusive.