Nipples may invert for many reasons. It can occur from birth or can develop throughout life. It can be a cosmetic problem and also interfere with breast feeding.
Most often inversion has no underlying cause but can represent a disease process within the breast tissue such as inflammation (mastitis) or within the milk ducts (duct ectasia). Importantly, it can also be associated with underlying presence of breast cancer.
Due to this associations, it is always advisable for Dr Rory to conduct a full breast examination and order any imaging needed to exclude these treatable conditions first. If no underlying cause is found, inverted nipples can be treated surgically.