Mastitis is defined as an inflammation of the breast and may or may not be accompanied by infection. It usually affects fertile women but can be seen at all ages and even in males. Mastitis is commonly divided into two groups: lactational mastitis which occurs in breastfeeding women, and non-lactational mastitis. A timely diagnosis and correct management is essential to avoid complications. In this review, we assess different types of inflammations of the breast and elucidate important differential diagnoses, such as inflammatory breast cancer.