The earliest stage breast cancers are stage 0 (carcinoma in situ). It then ranges from stage I (1) through IV (4). As a rule, the lower the number, the less the cancer has spread. The breast cancer staging system, called the TNM system, is overseen by the American Joint Committee on Cancer (AJCC). The AJCC is a group of cancer experts who . The various types of Breast Cancer Stages. Knowing the stage helps determine the best way to contain and eliminate the breast cancer. TNM System Of Staging.