Multimodal imaging changed clinical decision‐making: A rare mediastinal yolk sac tumor infiltrating the heart and follow‐up.

Background: Primary yolk sac tumor of the mediastinum is an extremely rare and highly malignant neoplasm, affecting mainly young men. Method and result: This case report describes a 60‐year‐old man with a mediastinal yolk sac tumor and infiltrating the heart. A large mobile mass was found in the right atrium by transthoracic echocardiography, and myxoma was suspected. However, contrast‐enhanced ultrasonography imaging revealed a remarkable enhancement in the mass. Highly metabolized mass was not only found in the right atrium, also in superior vena cava and right superior mediastinum by whole‐body positron emission tomography‐computed tomography. Supraclavicular lymph node biopsy confirmed the tumor as a primary mediastinum yolk sac. The tumor started to shrink during chemotherapy and AFP levels decreased. This patient significantly benefited from the chemotherapy. Conclusion: Multimodal imaging plays a vital role in the diagnostic workup and management for cardiac mass. [ABSTRACT FROM AUTHOR]