Case report: a rare case of primary lung tumour with local intra-atrial invasion.

[BACKGROUND] Cardiac tumours are rare, with the majority arising as metastases from non-cardiac sources. Lung cancer is among the more frequent malignancies to metastasize the heart, but direct invasion of the left atrium via the pulmonary veins remains uncommon. Differentiating between benign tumours, thrombus, and malignant extension can be challenging, and multi-modality imaging plays a key role.

[CASE SUMMARY] A 69-year-old woman with chronic obstructive pulmonary disease and hypertension was under investigation for a suspected primary lung malignancy with adrenal metastases. Computed tomography (CT) of the thorax demonstrated a possible left atrial thrombus. Subsequent transthoracic echocardiography revealed a large, mobile left atrial mass, initially thought to represent an atrial myxoma due to its stalk-like appearance and prolapse into the mitral valve. However, review of cross-sectional imaging raised concern for malignant invasion. Cardiac magnetic resonance imaging (MRI) confirmed a right middle lobe lung mass with direct extension into the right upper pulmonary vein and left atrium. The absence of atrial wall attachment was atypical for myxoma and supported tumour invasion. The patient was managed with best supportive care following multi-disciplinary discussion and sadly passed away within 6 months.

[DISCUSSION] This case highlights the diagnostic challenges of intracardiac masses and emphasizes the importance of integrating echocardiography with advanced imaging modalities.