Granulomatous mastitis is a rare condition in which the breast becomes infected and inflamed, developing a mass of tissue which is sometimes mistaken for a cancerous growth. Diagnosis of granulomatous mastitis is complicated by the fact that the condition mimics breast cancer, which means that a doctor may require several different tests to confirm a diagnosis and decide on the best treatment plan. This condition most commonly appears in the wake of a pregnancy, emerging as much as a year and a half after the pregnancy.

In granulomatous mastitis, women experience galactorrhea, in which milk flows freely from the breast, along with tenderness in the breast and inflammation which can cause the breast to feel hot to the touch. If granulomatous mastitis is allowed to progress, the breast can become wrinkled and pitted as the infection continues to grow inside.

During a breast exam, a doctor will usually be able to feel a mass inside the breast. This mass is actually a granuloma, a spontaneous collection of immune cells, not a tumor, but it can feel quite similar to a tumor. Women may also find the mass on a breast self-exam. The doctor may recommend testing such as an imaging study to look inside the breast and a biopsy to examine cells taken from the mass of tissue. The biopsy result will show that the mass is granulomatous in nature.

Treatment for granulomatous mastitis can include surgery to remove the granuloma and drain the wound. The patient is also given steroids to combat the inflammation. If granulomatous mastitis resolves successfully after treatment, there is a 50% chance that it will recur. One of the major problems with the treatment of this condition is that long-term steroid use can have serious side effects, but the only way to successfully get rid of granulomatous mastitis is to put a patient on a long coarse of steroids. Treatment must balance the need to resolve the inflammation with a desire to avoid causing complications for the patient.

The cause of granulomatous mastitis is not understood. Some researchers have suggested that it may be linked to breastfeeding, and that it is simply a more extreme form of the mastitis or inflammation of the breast which some breastfeeding women experience. Others suggest that it may be connected with the use of hormonal contraception, since it often appears after breastfeeding is concluded and a woman has started taking hormones to prevent an additional pregnancy.