BREAST CANCER Breast cancer is when breast cells mutate and become cancerous cells that multiply and form tumors. Signs of breast cancer may include a lump in the breast, a change in shape. Let's change the world together Share this content Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window