The determination of whether your cancer is invasive or noninvasive (in situ), the information gathered from your medical history and physical examination, as well as an evaluation of your initial breast imaging (mammogram, ultrasound, and or breast MRI) are all considered when identifying your breast cancer’s clinical stage. Once that stage is identified, your physician will be able to suggest the most appropriate treatment options.
Noninvasive Cancer Staging
Noninvasive breast cancer is classified as Tis, where “is” stands for in situ, or “in place.” In situ cancers, which are contained and do not spread to lymph nodes or outside the breast, are referred to as “stage 0.”
Invasive Cancer Staging
Invasive cancers have the potential to spread. The estimated size of the cancer and whether the cancer appears to have spread to the lymph nodes can be determined once the physician examines the breast and looks at the breast imaging, which usually includes a mammogram and ultrasound. If you have symptoms that suggest the cancer may have spread outside of the breast and lymph nodes, additional tests may be ordered. If you have bone pain, these tests may include a bone scan or PET scan.
The following TNM assignments are combined to form the stage of an invasive cancer:
- Tumor size (T)
- T1—Smaller than 2 cm (about 1 inch)
- T2—Between 2 and 5 cm
- T3—Larger than 5 cm
- T4—Tumors involving the skin and/or muscle
- Nodes (N): Lymph nodes under the arm and neck
- N0—No lymph node involvement
- N1—Lymph nodes under the arm are involved, but they are movable
- N2—Lymph nodes under the arm are involved and are stuck together
- N3—Lymph nodes under the arm and breastbone or near the collarbone are involved
- Metastases (M): Whether the cancer has spread outside the breast and underarm, or “metastasized”
- M0—No spread outside the breast and lymph nodes
- M1—Spread to any organ outside the breast and lymph nodes
For example, stage 1 is early-stage cancer where lymph nodes are not involved with cancer (T1N0M0). Stage 4 is when cancer has spread outside the breast and lymph nodes (any T, any N, but M1).
Clinical vs Pathological Staging
Keep in mind that the clinical stage may differ from the pathological stage because once the cancer has been surgically removed the pathologist can measure it precisely. The pathological stage may also differ if you receive chemotherapy or hormone-blocking therapy before your breast cancer surgery (known as neoadjuvant chemotherapy and neoadjuvant hormonal therapy).
Cancer staging fact sheet. National Cancer Institute website. Available at: www.cancer.gov/cancertopics/factsheet/detection/stagin
Cancer staging references. American Joint Committee on Cancer website. Available at: https://cancerstaging.org/references-tools/Pages/What-is-Cancer-Staging.aspx
Cancer staging guide. National Comprehensive Cancer Network website. Available at: www.nccn.org/patients/resources/diagnosis/staging.aspx