stage I breast cancer (... brest KAN-ser)
Stage I is divided into stages IA and IB. In stage IA, the tumor is 2 centimeters or smaller. Cancer has not spread outside the breast. In stage IB, small clusters of breast cancer cells (larger than 0.2 millimeter but not larger than 2 millimeters) are found in the lymph nodes and either: (1) no tumor is found in the breast; or (2) the tumor is 2 centimeters or smaller.