Other causes of infection include chronic mastitis and a rare form of cancer called inflammatory carcinoma. In healthy women, mastitis is rare. However, women with diabetes, chronic illness, AIDS, or an impaired immune system may be more susceptible. About 1%-3% of breastfeeding mothers develop mastitis. Engorgement and incomplete breast emptying can contribute to the problem and make the symptoms worse. Chronic mastitis occurs in women who are not breastfeeding.