Breast is a specialized skin gland. Its primary function is to produce milk for the nutrition of the newborn. Till puberty, both male and female breasts are morphologically similar in appearance. But at puberty, the female breast undergoes hyperplasia under sex hormones. This leads to proliferation of ducts, acini and stroma. The functional unit of the breast is a lobule. Inflammation of the breast parenchyma is called mastitis. It may develop in females during lactation. Mastitis may be acute or chronic. It is usually caused by bacteria, which reach breast through either skin or ducts. The inflammation may lead to formation of abscess. A detailed discussion on the benign tumors and carcinoma of the breast has been provided in this chapter.