Purulent cardiac tamponade associated with necrotic mediastinal lymphadenopathy: Multimodality imaging of a presumed mediastinal-pericardial pathway.

Purulent pericarditis is an uncommon but potentially fatal condition that may rapidly progress to cardiac tamponade. Contiguous spread from adjacent thoracic disease is a recognized mechanism; however, imaging documentation of a presumed mediastinal-pericardial pathway in association with necrotic mediastinal lymphadenopathy remains uncommon. We describe the case of a 72-year-old man with recently diagnosed low-grade prostate adenocarcinoma and a concomitant radiologically suspected primary right upper lobe lung malignancy. Baseline FDG PET/CT performed on 19 March 2026 demonstrated intensely hypermetabolic right upper lobe pulmonary lesions and FDG-avid mediastinal lymphadenopathy, including a supracarinal nodal station with central photopenia and corresponding central hypoattenuation, suggesting pre-existing necrotic change. On 11 May 2026, the patient presented with progressive dyspnea, hemodynamic compromise, and echocardiographic evidence of cardiac tamponade. Urgent subxiphoid pericardiocentesis yielded grossly purulent material. Cytology showed abundant neutrophilic inflammatory material without evidence of malignant cells. Gram stain, aerobic and anaerobic bacterial cultures, blood cultures, fungal cultures, and mycobacterial testing did not identify a causative pathogen. Contrast-enhanced chest CT performed on 13 May 2026 because of rapid pericardial fluid re-accumulation demonstrated a right lower paratracheal/anterior supracarinal nodal conglomerate with more extensive liquefactive necrosis, superior vena cava infiltration, and close apparent contiguity with the superior pericardial recess. Associated circumferential pericardial effusion, pericardial thickening, and pericardial enhancement were consistent with active pericarditis. This case highlights the complementary role of FDG PET/CT and contrast-enhanced CT in suggesting a presumed mediastinal-pericardial route in a patient with recurrent purulent pericardial effusion and necrotic mediastinal lymphadenopathy.