Myocardial perfusion imaging is a nuclear medicine imaging technique that allows to make an approach to the coronary condition in patients with moderate probability to have coronary artery disease. ^99mTc MIBI myocardial perfusion is one of the most common techniques in nuclear medicine clinical practice. Extracardiac accumulation of the tracer is relatively common, and can be seen in certain tumors with high metabolic rate, due to the radiotracer’s mitochondrial preference. We present a case report of an unusual finding in a myocardial perfusion scan related to an abnormal uptake of the radiotracer in a mediastinal mass which was consistent with thymoma.