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Breast Cancer Classification & Stages: 0 Through 4

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Standardized information is necessary for the doctors to know about the content of cancer cells spread in the body. The American Joint Committee on Cancer (AJCC) TNM system is the most common system used to describe the Stages of Breast Cancer. The stage of the breast can be based on different factors. Factors like the Clinical Stage which contains the results of physical examination, biopsy, and imaging tests. The critical stage can be described by using the Clinical factor plus the results of surgery. This factor is known as the Pathological Stage. Pathologic staging is likely to be more accurate than clinical staging because it allows the doctor to get a firsthand impression of the extent of cancer.

TNM Staging System of Breast Cancer

The TNM staging system classifies cancer on the basis of their T, N, M Stages

  • The letter T describes the tumor size and spread of skin or to the chest of the wall under breast followed by number 0-4. The number described the content of wider the cancer tissue spread and a larger tumor breast.
  • 0-3 number of letter N describes the spread of lymph nodes near the breast. The number range tells how many lymph nodes are affected.
  • The letter M followed by a 0 or 1 indicates whether cancer has spread to distant organs, such as the lungs or bones.

Categories of Primary Tumor (T) of Breast

  • TX: Primary tumor cannot be assessed.
  • T0: No evidence of primary tumor found.
  • Tis: Carcinoma in situ (DCIS, LCIS, or Paget disease of the nipple with no associated tumor mass) is present.
  • T1: Tumor is 2 cm (¾ of an inch) or less across.
  • T2: Tumor is more than 2 cm but not more than 5 cm (2 inches) across.
  • T3: Tumor is more than 5 cm across.
  • T4: Tumor of any size is growing into the chest wall or skin. This includes inflammatory breast cancer.

Nearby Lymph Nodes Staging (N) of Breast Cancer

These Nearby Lymph nodes are based on examination under a microscope. Lymph nodes staging for breast cancer has changed due to emerging technology techniques evolved in medical sciences. Earlier, finding a large deposit of cancer cells in lymph nodes was useful but missed microscopic cancer cells were ignored. But in recent times, the latest methods have made it possible to find microscopic cancer cells.

Many questions arise from the researchers on microscopic small cancer cells. Some questions are given below:

  1. Do microscopic small cancer cells affect the prognosis as the larger deposit of cell do?
  2. How many cells of cancers needed to change the stage of prognosis or treatment plan?

The general agreement in the area of cancer cells are given below:

  • Cancer cells must contain at least 200 cells or be at least 0.2mm across (less than 1/100 of an inch).
  • An area of cancer metastasis less than 200 cells will not change the stage.
  • Abbreviation introduced to reflect the way of metastatic was detected.
  • Abbreviation i+ means that cancer cells were only seen with a special technique named Immunohistochemistry.
  • mol+ is used to reflect that cancer cells were only seen using a technique called PCR. these tiny cancerous cells also called Isolated tumor cells.
  • Spreading area of cancer cell in the range between 02mm-2mm, called Microstases.
  • Microstates change the N stage because larger then 2mm spread area affects prognosis.

Categories of Lymph Nodes Staging

NX: Nearby Lymph nodes can’t be accessed. e.g already removed.

N0: Cancer has not spread to nearby lymph

N0(i+): Tiny amounts of cancer are found in axillary (underarm) lymph nodes by using immunohistochemistry. The area of metastasis contains fewer than 200 cells and is smaller than 0.2 mm.

N0(mol+): Cancer cells cannot be seen in axillary lymph nodes using immunohistochemistry, but traces of cancer cells were detected using the PCR test.

N1: Cancer has spread to 1 to 3 axillary (underarm) lymph node(s), and/or tiny amounts of cancer are found in internal mammary lymph nodes (those near the breastbone) on sentinel lymph node biopsy.

N1mi: Micrometastases (tiny areas of cancer spread) are found in 1 to 3 axillary lymph nodes. The areas of metastasis in the lymph nodes are 2 mm or smaller in size (but contain at least 200 cancer cells or are
at least 0.2 mm in size).

N1a: Cancer has spread to 1 to 3 axillary lymph nodes with at least one area of metastasis larger than 2 mm.

N1b: Cancer has spread to internal mammary lymph nodes, but this spread could only be detected through sentinel lymph node biopsy and did not cause the lymph nodes to become enlarged.

N1c: Both N1a and N1b apply

N2: Cancer has spread to 4 to 9 axillary lymph nodes or cancer has enlarged the internal mammary lymph nodes (either N2a or N2b, but not both).

N2a: Cancer has spread to 4 to 9 axillary lymph nodes, with at least one area of metastasis larger than 2 mm.

N2b: Cancer has spread to one or more internal mammary lymph nodes, causing them to become enlarged.

N3: Any of the following statements applies:

N3a:  Cancer has spread to 10 or more axillary lymph nodes, with at least one area of metastasis larger than 2 mm. It has another condition that  Cancer has spread to the lymph nodes under the clavicle (collarbone), with at least one area of metastasis larger than 2 mm.
N3b:  Cancer is found in at least one axillary lymph node. It can be that cancer involves 4 or more axillary
lymph nodes (with at least one area of metastasis larger than 2 mm), and tiny amounts of cancer are found in internal mammary lymph nodes on sentinel lymph node biopsy.

N3c: Cancer has spread to the lymph nodes above the clavicle with at least one area of metastasis larger than 2 mm.

Categories of Metastasis (M):

MX: The presence of distant metastasis cannot be assessed.
M0: No distant metastasis is found on x- rays or other imaging procedures or by physical exam.
cM0(i +): Small numbers of cancer cells are found in blood or bone marrow or tiny areas of metastasis (0.2 mm or smaller) are found in any lymph nodes.
M1: Spread to distant organs is present. (The most common sites are bone, lung, brain, and liver.)

Breast Cancer Stages

Once the T, N, and M categories have been determined, this information is combined in a process called Breast Cancer Stage grouping. There are four stages of Breast Cancer 1, 2, 3, and 4 with its subtypes. Type 0Non-invasive type of cancer. All stages with details are explaining below:

Breast Cancer Stage 0 (Tis, N0, M0 ):

Ductal Carcinoma in Situ(DCIS) is considered as Stage 0, the earliest stage of cancer. In this stage, cancerous cells limited to the duct and not spread in the surrounding tissues of the breast. Lobular carcinoma in Situ (LCIS) also considered as stage 0 cancer but according to doctors, it is not a practical type of cancer. Paget Disease, in which no underlying tumors, also considered as Stage 0.

Breast Cancer Stage 1:

This stage is further classified into two stages called Stage 1A, 1B.

Stage 1A (T1, N0, M0 ):

The tumor is 2 cm (about ¾ of an inch) or less across (T1) and has not spread to lymph nodes (N0) or distant sites (M0).

Stage 1B (T0 or T1, N1mi, M0):

The tumor is 2 cm or less across (or is not found) (T0 or T1) with micrometastases in 1 to 3 axillary lymph nodes (cancer in the lymph nodes is greater than 0.2 mm across and/or more than 200 cells but is not larger than 2 mm) (N1mi). Cancer has not spread to distant sites (M0).

Breast Cancer Stage 2:

This stage of breast cancer also classified in two more further stages for clarification.

Stage 2A:

In this stage, one of the following conditions would be satisfied to declare it in stage 2 breast cancer. Cancer has not spread to distant sites.

  • The tumor is 2 cm or less across
  • It has spread to 1 to 3 axillary lymph nodes, with cancer in the lymph nodes larger than 2 mm across.
  • Tiny amounts of cancer are found in internal mammary lymph nodes on sentinel lymph node biopsy (N1b).
  • It has spread to 1 to 3 lymph nodes under the arm and to internal mammary lymph nodes.
  • The tumor is larger than 2 cm across and less than 5 cm (T2) but hasn’t spread to the lymph nodes (N0).

Stage 2B:

In this stage, one of the following applies. On fulfilling this, stage to be called Stage 2B Breast Cancer.

  • The tumor is larger than 2 cm and less than 5 cm across (T2). It has spread to 1 to 3 axillary lymph nodes and/or tiny amounts of cancer are found in internal mammary lymph nodes on sentinel lymph node biopsy (N1). Cancer has not spread to distant sites (M0).
  • The tumor is larger than 5 cm across but does not grow into the chest wall or skin and has not spread to lymph nodes (T3, N0). Cancer has not spread to distant sites (M0).

Breast Cancer Stage 3:

In this stage, again further classifies into three more classifications for clarification.

Stage 3A:

One of the following condition fulfill, then cancer will be on the 3rd Stage.

  • The tumor is not more than 5 cm across (or cannot be found) (T0 to T2). It has spread to 4 to 9 axillary lymph nodes, or it has enlarged the internal mammary lymph nodes (N2). Cancer has not spread to distant sites (M0).
  • The tumor is larger than 5 cm across but does not grow into the chest wall or skin (T3). It has spread to 1 to 9 axillary nodes, or to internal mammary nodes (N1 or N2). Cancer has not spread to distant sites (M0)

Stage 3B:

The tumor has grown into the chest wall or skin (T4), and one of the following statements applies:

  • It has not spread to lymph nodes (N0).
  • It has spread to 1 to 3 axillary lymph nodes and/or tiny amounts of cancer are found in internal mammary lymph nodes on sentinel lymph node biopsy (N1).
  • It has spread to 4 to 9 axillary lymph nodes or it has enlarged the internal mammary lymph nodes (N2). Cancer has not spread to distant sites (M0).

Note: Inflammatory breast cancer is classified as T4 and is stage IIIB unless it has spread to distant lymph nodes or organs, in which case it would be stage IV.

Stage 3C:

The tumor is any size (or cannot be found), and one of the following statements applies:

  • Cancer has spread to 10 or more axillary lymph nodes (N3).
  • Cancer has spread to the lymph nodes under the clavicle (N3).
  • Cancer has spread to the lymph node above the clavicle (N3).
  • Cancer involves axillary lymph nodes and has enlarged the internal mammary lymph nodes (N3).
  • Cancer has spread to 4 or more axillary lymph nodes and tiny amounts of cancer are found in internal mammary lymph nodes on sentinel lymph node biopsy (N3). Cancer has not spread to distant sites (M0).

Breast Cancer Stage 4:

Cancer can be any size (any T) and may or may not have spread to nearby lymph nodes (any N). It has spread to distant organs or to lymph nodes far from the breast (M1). The most common sites of metastasis are the bones, liver, brain, and lung.

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