Direct left atrial invasion by lung cancer through the pulmonary vein: a case report of a rare cause of sylent systemic embolization.

Background: Intracardiac extension of lung cancer through the pulmonary veins is an uncommon but clinically significant manifestation, often associated with advanced-stage disease and poor prognosis. Case summary: We report the case of a 58-year-old heavy smoker who presented with rapid weight loss, asthenia, and food intolerance. Imaging revealed a large necrotic right lower lobe mass with direct invasion into the left atrium via the right inferior pulmonary vein, extending to the mitral valve. Despite the extensive cardiac involvement, the patient remained haemodynamically stable. Echocardiography showed a mobile intra-atrial mass without significant mitral obstruction but with high embolic potential. Multiple visceral infarcts were noted in the spleen and kidneys. The presence of brain metastases, bilateral adrenal involvement, and mediastinal lymphadenopathy confirmed advanced stage IV disease. The patient was deemed inoperable and referred for palliative care. Discussion: This case highlights a rare yet critical route of cardiac invasion in lung cancer. The combination of direct left atrial involvement and silent systemic embolization underscores the importance of multimodal imaging in diagnosis and risk assessment. Despite the absence of mitral obstruction, the presence of a hypermobile intracardiac mass should prompt consideration of embolic complications.