The term nonpuerperal mastitis describes inflammatory lesions of the breast occurring unrelated to pregnancy and breastfeeding.

It is sometimes equated with duct ectasia, but other forms can be described.

Duct ectasia

Duct ectasia - literally (lactiferous) duct widening is a very common and thus rather unspecific finding, increasing with age.

Subareolar abscess

Also called Zuska's disease (only nonpuerperal case), is a frequently aseptic inflammation and has been associated with squamous metaplasia of lactiferous ducts.

Granulomatous mastitis

Characteristic for granulomatous mastitis are multinucleated giant cells and epithelioid histiocytes around lobules. Often minor ductal and periductal inflammation is present. The lesion is in some cases very difficult to distinguish from breast cancer.

Comedo mastitis

Comedo mastitis is a very rare form similar to granulomatous mastitis but with tissue necrosis. Because it is so rare it may be sometimes confused with comedo carcinoma of the breast although the conditions appear to be completely unrelated.