Left Atrial Mass as the Initial Presentation of Poorly Differentiated Nonsmall Cell Lung Carcinoma.

BACKGROUND: Lung carcinoma is a leading cause of cancer-related mortality globally. Although metastasis to the bone, brain, and adrenal glands is common, secondary cardiac involvement is exceptionally rare, particularly within the left atrium. CASE PRESENTATION: A 62-year-old female patient, a known case of hypothyroidism, presented with a 6-month history of class II dyspnea on exertion and easy fatigability. She also reported a 2-month history of giddiness, chest discomfort, and weight loss. Initial 2-dimensional echocardiography revealed a large left atrial mass, suspected to be a tumor thrombus. Subsequent diagnostic evaluations, including a chest computed tomography scan and positron emission tomography, identified a primary lung carcinoma. A bronchoscopic biopsy confirmed poorly differentiated nonsmall cell lung cancer. CONCLUSIONS: This case highlights the importance of integrating multimodal imaging to accurately diagnose atypical intracardiac masses. It also emphasizes the clinical necessity of including metastatic lung malignancy in the differential diagnosis when an intracavitary cardiac mass is discovered.