RESUMEN
Sternalis muscle is an anatomical variation that is considered as a dilemma for surgeons and radiologists whereas a matter of interest for anatomists. It is found occasionally in the human on the anterior aspect of the thorax, superficial to the pectoralis major muscle. During routine cadaveric dissection for undergraduate medical students, presence of sternalis muscle was detected in a 60 years old mate cadaver. This rare anomaly has puzzled radiologists and surgeons in confirming diagnosis, missing it completely or mistaking it for a tumor on mammography or CT scan as it may mimic a malignant mass lesion on the medial aspect of craniocaudal mammograms. A detailed description of this important variation is needed in the text books for radiologists and surgeons