[4] It travels downward on the inside of the rib cage, approximately 1 cm from the sides of the sternum,[3] and thus medial to the nipple.

It runs deep to the abdominal external oblique muscle, but superficial to the vagus nerve.

In adults, the internal thoracic artery lies closest to the sternum at the first intercostal space.

[1] Plastic surgeons may use either the left or right internal thoracic arteries for autologous free flap reconstruction of the breast after mastectomy.

Usually, a microvascular anastomosis is performed at the second intercostal space to the artery on which the free flap is based.