Venous drainage is mainly to the axillary vein, but also to the internal thoracic, lateral thoracic, and intercostal veins.

The venous drainage of the breast corresponds to the named vessels of the arterial supply.  The drainage is via branches of the internal mammary vein (1), thoracoacromial vein (2),  lateral thoracic vein (3), thoracodorsal vein (4), and the branches of the intercostal veins (5).  Courtesy Ashley Davidoff MD 78378pb09a03b

Applied Anatomy

         Normal engorgement of the veins occurs during lactation, but also occurs in congestive failure.  The veins of the breast are sometimes utilized as collateral vessels when the superior vena cava is obstructed.

This is a CTscan of a middle aged female who shows thickening of the skin of the right breast.  She has carcinoma of the breast and has had radiation. What else do you see that is unusual?  See next image.  Courtesy Ashley Davidoff MD 38074

This image of the same patient is a section more inferior showing extensive collaterals in the left breast of which only part is visible.  Note that the patient also has ascites around the liver.  Courtesy Ashley Davidoff MD   38078