A unilateral rectus sternalis muscle was observed in a 80-year-old male cadaver. Located on the right side, the muscle took origin by a small fleshy belly from the lower part of pectoral fascia, at the level of 7 th costal cartilage. The fusiform muscle belly tapered into a thin delicate tendon at the level of 4 th costal cartilage, continued, for a short distance along right sternal margin, before crossing the sternum from right to left over the sternal angle and the left clavicle to merge with the sternal head of left sternocleidomastoid muscle [Table/ Fig-1 The sternalis muscle, an uncommon anatomical variant of the chest wall musculature, though perhaps well known to anatomists, is quite unfamiliar to clinicians and radiologists despite attempts to highlight its clinical importance in recent years. During routine dissection for undergraduate medical teaching, in the department of anatomy, we came across two cases of sternalis muscle. The first was a unique case of unilateral right sternalis with contralateral insertion on the left sternocleidomastoid, and the second case where bilateral presence of the muscle was noted with ipsilateral insertion. The former was supplied by medial pectoral nerve and the latter by lower intercostal nerves. Usually present between the pectoral and superficial fasciae, wide ranging prevalence and morphology have been attributed to this muscular variant. Opinions differ on its development and nerve supply. Its presence can be misdiagnosed as a wide range of benign and malignant anterior chest wall lesions and tumours, but it is also of great use as a pedicle flap or flap microvascular anastomosis in reconstructive surgeries of anterior chest wall, head and neck and breast. In this paper, two cases of sternalis muscle which presented very differently from each other are discussed.
Case 2Bilateral sternalis muscle was observed in a 70-year-old male cadaver. Muscles on both sides, roughly fusiform in shape, had a fleshy origin from external oblique aponeurosis at the level of seventh costal cartilage. The muscles became tendinous near the sternal angle, continued upwards and crossed the clavicle, to insert into the sternal head of ipsilateral sternocleidomastoid. Both muscles were innervated by lower intercostal nerves [Table/ Fig-2].