Paromastia, also known as polymastia, polymastia or ectopic breast, is a congenital developmental abnormality. In mammals, during the sixth week of embryonic life, two bulges called “mammary lines” are formed from the axilla to the groin, and multiple pairs of breast primordia appear on the mammary lines. If a pair of breast primordia does not atrophy and continues to develop, paramomastia will be formed after birth. The incidence of parametrium is 1% to 6% in women and occasionally in men. They are most common in the axilla and anterior axillary line, followed by the chest wall and groin, but can also be found on the thighs, arms, perineum, buttocks, etc. To date, rare areas outside the “breast line” include the cheeks, ears, back of the neck, arms, outer thighs, buttocks, perianal area, index finger, etc. Depending on the shape of the parametrium, there are two types of parametrium: complete and incomplete. Complete parametrium means that the nipple, areola or gland is fully developed; while incomplete parametrium means that one of the nipple, areola or gland is defectively developed. The incidence of incomplete parametrium is significantly higher than the incidence of complete parametrium. Sometimes incomplete parametrium is often misdiagnosed as lipoma, subcutaneous cyst, lymphadenitis, lymphatic nodules, fibroma, metastatic cancer, etc. because of the lack of nipple or areola structures. Parametrium is an atrophied and degenerated organ in the human body, which has no obvious function and generally does not grow with human development. However, the parametrium contains some breast glandular tissue and can become swollen or painful during menstruation; lactation can occur during lactation. Like normal breasts, parametrial breasts can also get diseases such as fibroadenoma or breast cancer, but the chances of this happening are very small. However, if the symptoms of the parametrium are obvious and difficult to tolerate or if the parametrium is large and affects the aesthetics, it can be surgically removed. Since the parametrium also has the possibility of tumor, routine pathological examination should be performed after the removal of the parametrium to check whether there is breast cancer at the same time for timely treatment. Diagnosis of parametrial breast: 1. Localized elevation or subcutaneous swelling near the axilla or around the normal breast; 2. The possibility of fibroids should be thought of if movable hard nodes are palpated in the above masses. If there are hard nodes or hard lumps in the parametrial masses, and if they are adherent to the skin or the base, or if there are orange peel-like skin changes on the surface, the possibility of cancer should be considered. Parametrial breast should be distinguished from lipoma and sebaceous cysts, which are easier to distinguish from lipoma because of the high penetrating power of near infrared light on fat. The sebaceous cysts have clear borders and are mostly round in shape, and the NIR scan also shows images of different shades of gray, but the images disappear when the skin is pinched. Treatment: Complete parametrial glands and incomplete parametrial glands with nipple areola but no gland can be treated without any treatment. The structure of the glands and ducts of incomplete parammary glands without nipples and with glands is basically the same as that of normal breast tissue. –This retained milk will break down into a carcinogenic substance, lactic factor, which can cause breast cancer. Therefore, paramastectomy should be performed as early as possible before pregnancy.