Mastitis is inflammation of the breast occurring in different forms and having many causes, including infection, usually staphylococcus, injury, and mammary-gland disease. It most frequently occurs during lactation. The most common disease of the female breast is a group of benign conditions collectively called chronic cystic mastitis, in which the breasts contain painful nodules or cysts of a rubbery consistency. The conditions include adenosis (multiple nodules caused by glandular disease). Treatment consists of surgical procedures or drugs. Chronic cystic mastitis may be related to later development of breast cancer, and continued observation is necessary. Bovine mastitis, an infection of cows, is of economic importance in dairy farming.