Mastitis is infection of the breast tissue, which causes pain and swelling in the affected breast. Women with this condition may also experience fevers and chills. Usually, the condition affects women who are breast feeding and this is refereed to as lactation mastitis. However, mastitis may also occur in individuals who are not breastfeeding.

Although mastitis usually affects women who are in the first three months after birth, the condition can can arise at any point during breastfeeding.

The signs and symptoms of mastitis may occur suddenly and most typically include the following:

• Pain in the breast that may be ongoing or only occur during breastfeeding
• General feeling of malaise
• Swelling in the breast tissue
• Redness in the affected area, often in a wedge-shaped pattern
• Breast may be tender and warm to touch

Mastitis is diagnosed based on a physical examination and the presence of symptoms. The doctor also checks for an abscess, which can develop if the condition is not treated.

Inflammatory breast cancer

A rare form of breast cancer called inflammatory breast cancer can also cause swelling and redness in the breast and a doctor may arrange a mammogram and biopsy to eliminate any possibility of this condition.

These carcinomas account for around 1 to 4% of all breast cancers and usually affect women who are in their 40s or 50s. The breast is enlarged and indurated and also feels warm, painful and tender to touch. The skin of the affected breast is oedematous and has a characteristic “peau d’orange” appearance. The nipple may also be flattened, crusting, blistered or retracted. However, systemic symptoms such as fever and chills are not present, which helps to differentiate the condition from mastitis.

The risk of breast cancer is significantly lower in women who breastfeed than in those who do not and there is no increase in lifetime risk with increasing episodes of mastitis. However, mastitis can delay the diagnosis of breast cancer and therefore treatment, which can lead to a more negative patient outcome.

Women who are not completely free of all mastitis symptoms within 5 weeks of diagnosis should be thoroughly examined for the presence of breast cancer. The symptoms that should have resolved within this timeframe include nipple discharge, hardness or lumps in the breast, redness and swelling.

Some studies suggest that the risk for noninflammatory breast cancer is increased within a year of mastitis developing that is not related to pregnancy or breastfeeding. This form of mastitis is referred to as nonpuerperal mastitis. In cases of this condition, special follow-up care is recommended to carefully monitor patients using preventative screening techniques.

Due to the short time period between nonpeurperal mastitis and inflammatory breast cancer developing, experts suspect that precancerous lesions play a role in triggering inflammation rather than inflammation contributing to the development of cancer.