After a breast cancer diagnosis, the first number you'll hear is stage. Stage describes how much cancer is in your body and where it's located. It's how your oncology team decides what treatments to recommend.
Stage 0 (DCIS — ductal carcinoma in situ): abnormal cells are inside a milk duct but haven't spread. Often treated with lumpectomy plus radiation, sometimes mastectomy. Long-term survival is over 98%.
Stage 1: the tumor is small (under 2 cm) and either hasn't reached lymph nodes or only minimally. Treatment usually includes surgery, often radiation, and sometimes chemotherapy or hormone therapy depending on the tumor's biology.
Stage 2: tumor is larger (2–5 cm) or has spread to a few nearby lymph nodes. Treatment typically combines surgery, radiation, and systemic therapy (chemo, hormone therapy, or targeted therapy).
Stage 3: tumor is larger than 5 cm or has spread extensively to lymph nodes or chest-wall tissue. Treatment is multimodal — often chemotherapy before surgery (neoadjuvant), then surgery, then radiation, then long-term hormone or targeted therapy.
Stage 4 (metastatic): cancer has spread to other organs (commonly bones, liver, lungs, brain). It's not currently curable but is highly treatable. Modern targeted therapies and immunotherapy let many patients live for many years with good quality of life.
Beyond stage, your pathology report includes biology that changes treatment: ER/PR status (hormone receptors), HER2 status, Ki-67 (growth rate), and sometimes Oncotype DX (a genomic test that predicts chemotherapy benefit). Two patients with the same stage can have very different treatments based on biology.
Bring your full pathology report to your first oncology visit and ask the oncologist to walk through it line by line. If anything is unclear, ask for a second opinion — second opinions are standard in breast cancer and covered by almost all insurance plans.