Constrictive Pericarditis Due to Metastatic Squamous Cell Carcinoma

BACKGROUND: Constrictive pericarditis is an uncommon but serious condition typically caused by idiopathic inflammation, prior cardiac surgery, or radiation. Malignancy is a rare etiology. CASE SUMMARY: A 62-year-old man with a history of tongue squamous cell carcinoma on long-term pembrolizumab presented with dyspnea, orthopnea, leg swelling, and ascites. Multimodal imaging revealed nodular pericardial thickening and constrictive physiology. Given lack of improvement on anti-inflammatory therapy and need to differentiate between metastatic disease versus immunotherapy-related inflammation, surgical pericardiectomy with biopsy was pursued. Histopathology confirmed poorly differentiated metastatic carcinoma invading the myocardium. Owing to poor prognosis, care was transitioned to hospice. DISCUSSION: Malignant pericardial involvement with constriction is a rare but important diagnostic consideration, particularly when atypical features or poor response to therapy are present. Immune checkpoint inhibitor-associated pericarditis can mimic malignant involvement, complicating noninvasive diagnosis. TAKE-HOME MESSAGE: When advanced imaging cannot definitively distinguish between immune-mediated and malignant pericarditis, tissue diagnosis is necessary.