The Mayo Clinic said that Paget's disease of the breast (also called Paget’s disease of the nipple) is a rare form of breast cancer. It starts on the nipple and extends to the dark circle of skin (areola) around the nipple. It isn't related to Paget's disease of the bone.
According to WebMD, Paget's disease of the breast almost exclusively occurs in women. However, rare cases have been recorded in men. The National Cancer Institute (NCI) reported more than 95 percent of people with this condition also have underlying breast cancer.
Scientists aren’t exactly sure what causes Paget disease of the breast, but there are two major theories.
One possibility, said BreastCancer.org, is cancer cells start growing inside the breasts’ milk ducts and make their way to the nipple surface. This could explain why many with Paget's disease of the breast have a second area of cancer within the breast.
The other theory, said NCI, suggests skin cells of the nipple spontaneously become Paget cells. This is supported by the rare cases of Paget disease in which there is no underlying breast cancer, and the cases in which the underlying breast cancer is separate from the Paget disease.
Johns Hopkins Medicine listed symptoms to include redness and irritation of the nipple and/or areola; crusting and scaling of the nipple area; bleeding or oozing from the nipple/areola; and burning and/or itching of the nipple/areola. Mayo Clinic said others include a flattened or turned-in nipple; a lump in the breast; and thickening skin on the breast.
Paget's disease of the breast usually requires surgery. The type depends on the skin condition around the nipple and the advancement of the underlying cancer.
BreastCancer.org wrote mastectomy may be needed if the underlying breast cancer is invasive to reduce the risk of any cancer cells remaining in the breast.
A modified radical mastectomy is one type. NCI said the surgeon removes the breast, the lining over the chest muscles, and some of the lymph nodes under the arm.
A simple mastectomy may be best in cases where underlying breast cancer isn’t invasive.