Stage 1 breast cancer
Stage 1 breast cancer means cancer cells invade the breast tissue surrounding them. Stage 1 breast cancer consists of two sub-categories that are 1A and 1B.
Women with stage 1A breast cancer have breast cancer with: a tumor with a diameter not exceeding 2 centimeters (cm) and that has not spread outside the breast tissue.
Women in stage 1B have invasive breast cancer in which cancer cells have grown into clusters that are between 0.2–2 (millimeter) mm in diameter and may also be found in the lymph nodes. In most cases, 2B is a stage where a tumor is not greater than 2 cm and grows in the breast alongside small groups of cancer cells that develop in the lymph nodes.
If the cancer is ER+ or PR+, it is still likely to be classified as stage 1A cancer by a doctor. Microscopic invasion is where cancer cells began spread outside the lining or lobule of the milk duct. If there is a microscopic invasion, doctors may still classify cancer as breast cancer in stage 1 provided that these clusters of cells do not measure more than 1 mm.