This 43-year-old woman was rushed to ER because of the sudden onset of substernal chest tightness accompanied by cold sweats, which lasted more than 30 minutes. Past medical history (PMH) was significant for hyperlipidemia for five years, excision of retroperitoneal leiomyosarcoma, along with segmental colectomy and total hysterectomy without evidence of tumor metastasis six years ago, and s/p radiotherapy and chemotherapy for stage IV leiomyosarcoma involving the spleen, right pelvic wall, and cardiac right ventricle (RV)as detected by CT scan two years ago. One month prior, she also had duodenal bleeding due to tumor metastasis. Her family history was positive for atherosclerotic coronary heart disease (CHD) (mother 65 and two brothers in their 40’s). On arrival, she appeared obese (BMI 31.1), pale, and in respiratory distress. BP measured 120/75 mmHg, PR 102/min (regular), and RR 25/min. There was no jugular venous distension. Heart sounds were distant, and PMI was not visible, but a grade 2/6 systolic murmur was audible along the left 2nd and 3rd sternal border. Lungs were clear. The abdomen showed previous surgical scars. Laboratory data revealed Hb 9.9 g/dL, Plt 196 K/uL, WBC 21,230/uL with 87% Neu, INR 1.07, and Troponin-I 0.01 ng/mL, CK-MB 2.3 U/L, BUN 12 mg/dL and Cr. 0.86 mg/dL. ECG exhibited ST-segment elevation and T wave inversion in V1-V4 alongside intraventricular conduction defect (IVCD), suggesting acute myocardial infarction involving the proximal left anterior descending artery (LAD). Accordingly, the care team prompted cardiac catheterization with coronary angiography; It revealed insignificant CHD, i.e., except for 30% occlusion in LCX, LM, LAD, and RCA were patent. However, LAD and RCA notably supplied blood to an ill-defined, highly vascularized RV mass. Echocardiography estimated the RV tumor to be 2-3cm in thickness, extending from the RV apex to the RV outflow tract (RVOT)(confirmed by CT scan), which protruded into the pulmonary artery during the systolic phase, causing mild and pulmonary stenosis. The ECG ST-segment elevation in V1-V4 resolved after supportive hydration therapy. Under the diagnosis of acute coronary syndrome presumed to be due to a coronary artery steal phenomenon related to an RV metastatic leiomyosarcoma, the care team consulted the oncology and surgical specialists.