First of all, both gynecomastia and breast cancer are mainly manifested by lumps on the breast. The main difference is that male breast development is usually a lump on both breasts, while breast cancer is usually a single lump, and male breast development is usually seen in adolescent males, usually in their twenties or thirties, while male breast cancer has a very low incidence rate, with a high incidence in the fifties. In addition, on examination, breast development appears as a thickened gland on ultrasound, while breast cancer typically appears as a hypoechoic breast, surrounded by burrs, with unclear borders and echogenic attenuation. In addition, on palpation, the lump of breast development is usually tough and has a certain boundary when touched, while breast cancer is usually a harder lump and less mobile. Most of the treatment for gynecomastia does not require treatment, very few of them take medicine, and if the result is not good, surgery can be considered, while treatment for breast cancer usually requires mastectomy, and later chemotherapy or even radiotherapy may be needed. From the point of view of the treatment effect, male breast development is very effective and generally has no major consequences and is not life-threatening, while male breast cancer is a tumor of very high malignancy and generally has a very high mortality rate.