It is spread through blood or by the lymphatic vessels. Cancer is a disease when abnormal cells in some organ or tissue, in this case the breast, grow out of control and increase in number. When these cells form a mass it is called a tumor which can enlarge locally and invade and destroy normal tissue around it, or it can spread to different body parts as described above. Some breast cancer is hormone dependent and test can show if a tumor has hormone receptor in its cells, in other words, it may be an estrogen receptive positive cancer. That means the cancer uses the hormone estrogen to grow.
Hormone therapy can interrupt the flow of estrogen to starve and kill the tumor.
Tamoxifen is the main anti-estrogen drug. The tumor usually arises from the cells of milk sacs or milk ducts, although malignant tumors occasionally arise from the supporting structure. Even a cancer arising from the sacs or ducts may show variation. It may grow into the duct canal and signal its presence early with bleeding from the nipple. Alternatively, it may grow into the breast tissue as a mass which is usually very hard, but may, with some kinds of tumors, be soft.