Rectus thoracis bifurcalis: a new variant in the anterior chest wall musculature.

A cadaveric study was undertaken to report the incidence of sternalis muscle in cadavers of Asian origin. A total of 88 cadavers were studied over a period of six years and the sternalis was reported only in a single case and that too unilaterally. The accessory muscle was discovered in the right pectoral region in a 40-year-old male cadaver. The muscle emanated from the external oblique aponeurosis of abdomen confirming its origin from the ventral longitudinal sheet of muscle. The muscle was fleshy throughout its extent except at the ends where they were aponeurotic. At the sternal angle, the muscle displayed "Y" shaped configuration and merged with the respective sternocleidomastoid muscle. The innervation was derived from the third intercostals nerve. We intend to highlight a few points through this study. Firstly, we found a paucity of studies undertaken to describe the incidence of sternalis muscle. Further, the studies present in anatomical archives are mainly case reports. Secondly, this muscle presents itself in varying configurations on radiological studies. The radiologist should acquaint himself with all these presentations, so that he can make accurate diagnosis of a breast mass. Thirdly, this muscle having more morphological relevance may be conveniently utilized for flap procedures of post mastectomy breast reconstruction. Lastly, the presence of this muscle may alter the depth at which the internal mammary lymph nodes are irradiated in case of carcinoma breast. Additionally, it should not be erroneously diagnosed as a mass which recurred on follow up of breast cancer patients. The present investigation endeavors to discuss the anatomical, embryological and clinical relevance of a rare accessory muscle of the anterior chest wall.