Conclusions

Intracardiac extension of malignant SFT is exceptionally rare and may mimic giant left atrial thrombus on echocardiography. Histopathological examination remains essential for definitive diagnosis, particularly in patients with known metastatic malignancy. Highly mobile left atrial neoplastic masses prolapsing through the mitral valve represent a medical and surgical emergency because of the risk of catastrophic systemic embolization and acute mitral inflow obstruction.

This case underscores the diagnostic limitations of imaging alone, the importance of pathological confirmation, the critical role of echocardiography in risk stratification, and the necessity of multidisciplinary management in complex cardio-oncologic presentations. Multimodality imaging, where feasible, combined with histopathological confirmation and multidisciplinary management, remains central to diagnosis and treatment, and long-term surveillance is warranted, given the recognized recurrence potential of malignant SFTs.