Oncotype DX®

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Oncotype DX®

Staging Breast Cancer

Most kinds of cancer use a staging system to define how serious the cancer is. The scoring system rates cancers from Stage I to Stage IV. Stage I is the least severe and Stage IV is the most severe. Three pieces of information are most important:

  1. Tumor Size
  2. Lymph Node Involvement
  3. Metastasis

This is also called the TNM system. T stands for Tumor size, N for Lymph Node Status, and M for Metastasis.

Tumor Size

The size of the tumor falls into one of four categories for staging:

  • T1 - the tumor is less than 2 centimeters (cm)
  • T2 - the tumor is between 2 cm and 5 cm
  • T3 - the tumor is more than 5 cm
  • T4 - the tumor is any size, but is also attached to the inside of the chest or skin

In general, the larger a tumor is, the more likely it is to have spread to nearby tissues or lymph nodes. However, some large tumors don't spread and are less aggressive than small tumors.

Oncotype DX test results can help figure out how aggressive a relatively small tumor is. Oncotype DX® testing should only be used for T1- or T2-sized tumors.

Lymph Node

People have about 500 to 600 lymph nodes throughout the body. There are clusters of lymph nodes in the underarms, groin, neck, chest, and abdomen. Lymph nodes drain extra fluid from the breasts. The first lymph node to drain a breast tumor is called the sentinel lymph node. After the sentinel node, breast tumor cells usually travel to other lymph nodes in the armpit. The more lymph nodes that have cancer cells, the more likely it is that the cancer cells have moved to other areas of the body.

Breast cancer staging says how many lymph nodes have cancer cells, and which ones:

  • N0 - no lymph nodes have cancer cells
  • N1 - the cancer has spread to the underarm lymph nodes (called axillary) on the same side as the cancer
  • N2 - tumor cancer cells are present in the axillary lymph nodes, or present in the internal mammary lymph nodes, on the same side as the tumor and fixed or attached to other structures
  • N3 - tumor cancer cells have spread to lymph nodes in the neck on the same side as the tumor or are present in the internal mammary lymph nodes AND are in the axillary lymph nodes

When there are no cancer cells in the lymph nodes (N0), it is called lymph node-negative cancer. The cancer is more likely to be confined to the breast and not to have spread. This lowers the chance of cancer coming back in the future. Oncotype DX test should only be used for lymph node-negative (N0) breast cancer.


Metastasis is when cancer cells have moved from where they started to other areas of the body. There are two main metastasis categories:

  • M0 - no metastasis past the underarm lymph nodes
  • M1 - metastasis to organs or lymph nodes beyond the underarm lymph nodes

When cancer comes back after treatment, it is called a cancer recurrence. Cancer comes back in two main ways. A local recurrence is when the cancer comes back in the same place as the first cancer. In the case of breast cancer, this would be recurrence in the same breast or inside the chest near the first tumor.

A distant recurrence, or metastasis, happens when cancer spreads to other parts of the body outside the breast. A breast cancer metastasis usually spreads to the lungs, bones, liver, or brain.

Oncotype DX testing calculates the chance of metastasis over the next 10 years. Oncotype DX should only be used for early-stage breast cancer without signs of metastasis (M0).

Next: Breast Tumor Characteristics