- Stage 1A: The tumor measures 2 cm or smaller (about the size of a pea or shelled peanut), and has not spread outside the breast.
- Stage 1B: Small clusters of cancer cells measuring no more than 2 mm, are found in the lymph nodes, and either there is no tumor inside the breast, or the tumor is small, measuring 2 cm or less.
At stage 1, TNM designations help describe the extent of the disease. (In the TMN system, T describes the size of the original tumor; lymph node -- N -- indicates whether the cancer is present in the lymph nodes; and metastasis -- M -- refers to whether cancer has spread to other parts of the body.) For example, there may or may not be cancer cells in the lymph nodes, and the size of the tumor may range from 1 cm to 2 cm. Most commonly, stage 1 breast cancer is described as:
- T: T1, T2, T3 or T4, depending on the size and/or extent of the primary tumor.
- N0: Usually, cancer has not spread to the lymph nodes
- M0: The disease has not spread to other sites in the body