Abstract Introduction Testis tumors constitute 1-2% of all malignant tumors in men. But it is the most common solid tumor in men between 15-35 years of age. Germ cell tumors constitute for almost 90% of all testis tumors. Intracardiac metastasis of testicular carcinomas is rare. We now report a case of a testicular germ cell tumor with right atrial metastasis. Case report A 30-year-old male patient was diagnosed with B-cell ALL.Chemotherapy and radiotherapy were completed in 2016. In January 2017, the patient applied to the hospital with pain in the right testicle.A mass detected and orchiectomy was performed.Pathologic examination revealed mixed germ cell tumor and B-cell ALL infiltration.Chemotherapy was started. The patient was admitted to our hospital with fever, in March 2018.Antibiotics were started but fever contuniued.Transthoracic echocardiography showed a large,hypoechogen,mobile mass in the right atrium.Then transesophageal echocardiography revealed a 2x3,3 cm mobile mass within the right atrium that prolapsed through the tricuspid valve into the right ventricle in diastole.We could not distinguish if it is a vegetation or a metastatic mass. The patient underwent cardiac surgery.Pathologic examination revealed mixed germ cell tumor metastasis. After the surgery, the patient was transferred to the intensive care unit because of sepsis. Antibiotics were expanded due to fever. Control transthoracic echocardiography and also transesophageal echocardiography showed a 1,8 x 0,6 cm mobile mass extending from the inferior vena cava into the right atrium and through the patent foramen ovale into the left atrium. One week after the surgery, a mass was detected in the transthoracic echocardiography. But no further examination was done. We thought that the mass may not have been completely removed in the the operation (residual tumor?). The patient was evaluated with the department of oncology and cardiovascular surgery. It was decided that reoperation would be very risky. Conclusion Metastatic tumors of the heart are seen more frequently than primary tumors. Although intracardiac metastasis of testicular germ cell tumors are rare (less than %1), it has been related to short survival. They may lead to the congestive heart failure, paradoxical systemic emboli and vena cava superior syndrome. Most cases in the literature are associated with right atrial mass. But in our case, the mass was extending from the inferior vena cava into the right atrium and through the patent foramen ovale into the left atrium. We wanted to share our experience and also wanted to discuss the treatment modality for similar patients. Abstract P1703 Figure.