We present the case of a 42-year-old female with a history of human epidermal growth factor 2 (HER2) receptor-positive breast cancer status post bilateral mastectomy with metastasis to the spine and to the brain, who underwent transesophageal echocardiography (TEE) after outpatient transthoracic echocardiography (TTE) was suggestive of right atrial thrombus in transit. TEE revealed an atrial mass with a pedunculated stalk attached to the inferior right atrium near the inferior vena cava with a necrotic center. The gene discussed is ERBB2; the disease is breast cancer.