The lateral costal branch (LCB) is a variation present in 15-30 % of the population. This blood vessel runs parallel and laterally to the internal thoracic artery from which it originates. Knowledge about the LCB is relevant for thoracic surgeons. In this study we present the findings from the dissection in a practical teaching exercise of the cadaver of a 62-year -old male. The thoracic contents were accessed by raising the anterolateral thoracic wall, the pulmonary pedicles were dissected and both lungs were removed. We observed bilaterally the trajectory of the LCB at the level of the medial axillary line parallel to the internal thoracic artery. On the right side, the LCB originates from the internal thoracic artery at the level of the first rib and extends to the eighth intercostal space, with a length of 26 cm and a caliber of 1.95 mm, communicating with the anterior and posterior intercostal arteries. The left branch originates from the internal thoracic close to their origin artery and extends until the sixth intercostal space, with a length of 14 cm and a caliber of 1.55 mm. it connects with the anterior and posterior intercostal arteries. On both sides the arteries were accompanied by a pair of satellite veins. The lateral costal arteries form part of the circulation of the thoracic wall, constituting an accessory arterial system with a trajectory parallel to the internal thorax and the aorta. Knowledge of it is relevant for invasive procedures, and myocardial revascularization procedure.
KEY WORDS: Lateral costal branch; Anatomical variation; Clinical anatomy.