HER2+ Early-Stage Breast Cancer

Staging

You may feel overwhelmed with all of the new information you’ve been receiving. However, understanding the stage and what it means will help put your cancer into perspective. Your managing physician will develop the best treatment plan for you after your stage is determined.

The staging system used for breast cancer was developed by the American Joint Committee on Cancer (AJCC). Known as TNM staging, this system uses the tumor (T), node (N) and metastasis (M) classification (see Tables 1 and 2). These tables share information based on the size and spread of disease. Your final stage will be determined after your doctor also considers other factors, such as tumor grade and biomarkers. These may include estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor-2 (HER2) status, and multi-gene panels, such as MammaPrint, Oncotype DX, PAM 50 (Prosigna) and Breast Cancer Index.

The T classification categories are the same for both clinical and pathologic staging and provide information on the size and extent of the tumor within the breast. Clinical T (described as cT) refers to the tumor size estimate based on physical/clinical examination and breast imaging; pathologic T (described as pT) refers to the size of the tumor when it has been removed and measured in the pathology laboratory.

Clinical staging for the N category (cN) describes the location and bulkiness of lymph nodes that seem to be malignant (from spread of the breast cancer) on physical examination. Location and extent of any cancerous lymph nodes provide clues regarding the likelihood that the breast cancer might have spread to other organs. The pathologic N category (pN) is determined postoperatively and describes how many lymph nodes are involved.

The M category indicates if the cancer has spread to another part of the body beyond the breast and local lymph nodes.

Breast biopsy and breast surgery tissue are examined by a specially trained doctor called a pathologist. The pathologist evaluates the breast tissue under the microscope and uses special stains/techniques to characterize the cancer. Breast cancers are classified according to subtypes based on molecular or genetic changes. Distinguishing between these subtypes is important because treatments and monitoring milestones, such as response to therapy and likelihood of disease relapse, vary by subtype. The pathology report on an invasive breast cancer will describe the grade (which is based on the microscopic features of tumor cell growth rate and aggressiveness), as well as the biomarkers ER, PR and HER2. All of this information contributes to the stage of your cancer and determining the best treatment options.

Ask your doctor to explain the stage and grade of your breast cancer. Understanding your diagnosis will help you make more informed treatment decisions.

Table 1. AJCC TNM System for Classifying Breast Cancer

Category Definition
Tumor (T)
TX Primary tumor cannot be assessed.
T0 No evidence of primary tumor.
Tis (DCIS) Ductal carcinoma in situ.
Tis (Paget) Paget disease of the nipple NOT associated with invasive carcinoma and/or carcinoma in situ (DCIS) in the underlying breast parenchyma (tissue).
T1
  T1mi
  T1a
  T1b
  T1c
Tumor ≤ (not more than) 20 mm in greatest dimension.
Tumor ≤ (not more than) 1 mm in greatest dimension.
Tumor > (more than) 1 mm but ≤ (not more than) 5 mm in greatest dimension.
Tumor > (more than) 5 mm but ≤ (not more than) 10 mm in greatest dimension.
Tumor > (more than) 10 mm but ≤ (not more than) 20 mm in greatest dimension.
T2 Tumor > (more than) 20 mm but ≤ (not more than) 50 mm in greatest dimension.
T3 Tumor > (more than) 50 mm in greatest dimension.
T4

  T4a
  T4b

  T4c
  T4d
Tumor of any size with direct extension to the chest wall and/or to the skin (ulceration or macroscopic nodules).
Extension to the chest wall.
Ulceration and/or ipsilateral (on the same side) macroscopic satellite nodules and/or edema (including peau d’orange) of the skin that does not meet the criteria for inflammatory carcinoma.
Both T4a and T4b are present.
Inflammatory carcinoma.
Node (N)
pNX Regional lymph nodes cannot be assessed.
pN0
  pN0(i+)

  pN0(mol+)
No regional lymph node metastasis identified or ITCs (isolated tumor cells) only.
ITCs (isolated tumor cells) only (malignant cell clusters no larger than 0.2 mm) in regional lymph node(s).
Positive molecular findings by reverse transcriptase polymerase chain reaction (RT-PCR); no ITCs (isolated tumor cells) detected.
pN1


  pN1mi
  pN1a
  pN1b
  
  pN1c
Micrometastases; or metastases in 1-3 axillary (armpit) lymph nodes; and/or clinically negative internal mammary nodes with micrometastases or macrometastases by sentinel lymph node biopsy.
Micrometastases (approximately 200 cells, larger than 0.2 mm, but none larger than 2.0 mm).
Metastases in 1-3 axillary (armpit) lymph nodes, at least one metastasis larger than 2.0 mm.
Metastases in ipsilateral (on the same side) internal mammary sentinel nodes, excluding ITCs (isolated tumor cells).
pN1a and pN1b combined.
pN2
  
  pN2a
  pN2b
Metastases in 4-9 axillary (armpit) lymph nodes; or positive ipsilateral (on the same side) internal mammary lymph nodes by imaging in the absence of axillary lymph node metastases.
Metastases in 4-9 axillary (armpit) lymph nodes (at least one tumor deposit larger than 2.0 mm).
Metastases in clinically detected internal mammary lymph nodes with or without microscopic confirmation; with pathologically negative axillary (armpit) nodes.
pN3






  pN3a
  
  
  pN3b
  
  pN3c
Metastases in 10 or more axillary (armpit) lymph nodes;
or in infraclavicular (below the clavicle) (Level III axillary) lymph nodes;
or positive ipsilateral (on the same side) internal mammary lymph nodes by imaging in the presence of one or more positive Level I, II axillary lymph nodes;
or in more than three axillary lymph nodes and micrometastases or macrometastases by sentinel lymph node biopsy in clinically negative ipsilateral internal mammary lymph nodes;
or in ipsilateral supraclavicular (above the clavicle) lymph nodes.
Metastases in 10 or more axillary (armpit) lymph nodes (at least one tumor deposit larger than 2.0 mm);
or metastases to the infraclavicular (below the clavicle) (Level III axillary) lymph nodes.
pN1a or pN2a in the presence of cN2b (positive internal mammary nodes by imaging);
or pN2a in the presence of pN1b.
Metastases in ipsilateral (on the same side) supraclavicular (above the clavicle) lymph nodes.
Note: (sn) and (f) suffixes should be added to the N category to denote confirmation of metastasis by sentinel node biopsy or FNA/core needle biopsy respectively, with NO further resection of nodes.
Metastasis (M)
M0 No clinical or radiographic evidence of distant metastases.
  cM0(i+) No clinical or radiographic evidence of distant metastases in the presence of tumor cells or deposits no larger than 0.2 mm detected microscopically or by molecular techniques in circulating blood, bone marrow, or other nonregional nodal tissue in a patient without symptoms or signs of metastases.

Table 2. Stages of Breast Cancer

Stage TNM Classification
0 Tis, N0, M0
IA T1, N0, M0
IB T0 or T1, N1mi, M0
IIA T0 or T1, N1, M0
T2, N0, M0
IIB T2, N1, M0
T3, N0, M0
IIIA T0-T3, N2, M0
T3, N1, M0
IIIB T4, N0-N2, M0
IIIC Any T, N3, M0

Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original and primary source for this information is the AJCC Cancer Staging Manual, Eighth Edition (2017) published by Springer Science+Business Media.

 

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