The lateral thoracic vein is a tributary of the axillary vein. It runs with the lateral thoracic artery and drains the serratus ventralis muscle and the Pectoralis major muscle. Normally, the thoracoepigastric vein exists between this vein and superficial epigastric vein (a tributary of femoral vein), to act as a shunt for blood if the portal system (through the liver) develops hypertension or a blockage. [WP,unvetted]. [ http://en.wikipedia.org/wiki/Lateral_thoracic_vein ]