Breast cancer is mainly composed of breast glands, ducts, fatty tissue and fibrous tissue. Each glandular lobe is divided into several lobules, and each lobule is composed of 10 to 100 vesicles. These vesicles are arranged closely around the small milk ducts, and the openings of the vesicles are connected to the small milk ducts. The ducts converge to form interlobular ducts, which further converge to form a duct of the entire lobe, also known as the milk duct. There are 15 to 20 milk ducts, which are arranged in a radial pattern with the nipple as the center, converging on the areola and opening at the nipple, called the milk ducts. The milk ducts are narrower at the nipple and then expand into a pot belly called the sinus of the milk duct, which has the role of storing milk. The opening of the ducts is lined with squamous epithelial cells and the narrowing is lined with migrating epithelium, while the ducts below the pot belly are lined with double columnar epithelium or single columnar epithelium. The glands secrete milk and the ducts transmit the milk to the nipple, while fatty and fibrous tissues surround the breast and the ducts to play a supporting role. 2. What is breast cancer Under normal circumstances, the glandular epithelial cells of the breast divide and grow in an orderly manner. However, at some point, for some reason, some cells undergo genetic mutation, and the cells proliferate out of control, showing disorderly and unrestricted malignant division and growth, thus evolving into adenocarcinoma cells. A large number of cancer cells proliferate and crowd into clusters in a disorderly manner, squeeze and invade and destroy the surrounding normal tissues and damage the normal structure of the breast, and then gradually breast cancer is formed. Therefore, breast cancer is a malignant tumor that occurs in the glandular epithelial tissue of the breast and is one of the most common malignant tumors in women. Many breast cancers begin as tumors on the surface cells of the milk ducts, while others develop as tumors on the lobules of the breast. Breast cancer includes invasive carcinoma of the breast and carcinoma in situ of the breast. Breast cancer has become the most prevalent malignant tumor among women worldwide, with about 1.2 million women suffering from breast cancer each year. In China, the incidence of breast cancer among women in large and medium-sized cities is the highest, and the incidence rate continues to rise, ranking first among female malignant tumors in Shanghai. The peak age of the disease is 45 to 55 years old, 10 to 15 years earlier than women in western countries, and the consultation time is quite late.