Breast Cancer (BC)

Staging

Staging is based on the TNM classification.

The most recent American Joint Committee on Cancer (AJCC) system, in effect since January 2018, has both a clinical and pathological breast cancer staging system.

7 key elements of information are used:

1. Tumor size (T)

Primary tumor (T):

Tx — insufficient data to evaluate the primary tumor

Tis — carcinoma in situ (ductal carcinoma in situ or Paget’s cancer)

T1 (includes T1a, T1b, and T1c) — a tumor is 2 cm or less in diameter

T2 — a tumor is 2–5 cm in size

T3 — a tumor is larger than 5 cm in greatest dimension

T4 (includes T4a, T4b, T4c, and T4d) — a tumor of any size that invades the chest wall or skin, including inflammatory breast cancer

2. Spread to nearby lymph nodes (N)

Morphological examination of at least 12 lymph nodes

Nx — insufficient data to evaluate regional lymph nodes

N0 — no signs of metastatic involvement of regional lymph nodes

N1mi — micrometastases

N1 — presence of metastases in 1-3 axillary lymph nodes and / or cancer found in the internal mammary lymph nodes by sentinel lymph node biopsy

N2 — cancer has spread to 4-9 lymph nodes under the arm, or the cancer has enlarged the internal lymph nodes of the breast

N3 — cancer has spread to 10 or more axillary lymph nodes, with at least one area of cancer spread greater than 2 mm or to subclavicular/supraclavicle lymph nodes with at least one area greater than 2 mm, or to 4 lymph nodes, with at least one area of cancer spread greater than 2 mm and to internal lymph nodes of the mammary gland

3. Spread (metastasis) to distant organs (M)

M0 — no distant metastases

M1 — presence of distant metastases

4. Estrogen receptor (ER) status

Do tumor cells have a protein called the estrogen receptor on their surface?

5. Progesterone receptor (PR) status

Do tumor cells have a protein called the progesterone receptor on their surface?

6. HER2 status

Do tumor cells produce too much HER2 protein?

Histological grade of tumor malignancy (G)

How tumor cells morphologically similar to normal cells?

Gx — Category G cannot be detected

G1 — Low grade (favorable variant)

G2 — Moderate grade

G3 — High grade of malignancy (unfavorable variant)