Tumor size is an important factor in breast cancer staging, and it can affect a person's treatment options and outlook. Tumors are likely to be smaller when doctors detect them early, which can make them easier to treat.

However, the size of the tumor is only one of the factors that doctors consider when staging a person's breast cancer. Other factors include the location of the tumor, whether it has spread outside of the breast, the appearance of the cancer cells, and the presence of hormone receptors.

In this article, we present a tumor size chart and discuss how tumor size affects cancer staging. We also cover other factors that contribute to staging, treatment, and a person's outlook.

Tumor size and breast cancer staging

Doctors determine the stage of cancer as part of their diagnosis. To confirm the stage of breast cancer, they assess a number of different factors, including tumor size. Doctors use a range of tests and examinations to evaluate the specific characteristics of a person's breast cancer. They use this information to assign values to the TNM staging system, where:

• T is the size of the main, or primary, tumor
• N is whether cancer has spread to nearby lymph nodes
• M is whether the cancer is metastatic, which means that it has spread to distant parts of the body

The overall stages of cancer range from 0 to IV. Stage 0 means that breast cancer is at a very early stage and has not yet spread. Stage IV is late-stage breast cancer, in which the cancer has spread to other parts of the body.

Every person's breast cancer is different, but its stage provides a general indication of a person's treatment options and outlook. People with early stage breast cancer are likely to have smaller tumors that are easier for doctors to treat. Larger tumors tend to indicate later-stage breast cancer, which may be more difficult to treat.

How are breast tumors measured?

Doctors measure the size of the primary breast cancer tumor at its widest point. They usually give the size in millimeters (mm) or centimeters (cm). According to the American Cancer Society (ACS), doctors use the following system to grade tumor size:

• TX: The doctor is unable to assess the primary tumor.
• T0: The doctor has not found evidence of a primary tumor.
• T1: The tumor is 2 cm (0.79 inches [in]) or less in diameter.
• T2: The tumor is more than 2 cm (0.79 in) but less than 5 cm (1.97 in) across.
• T3: The tumor is larger than 5 cm (1.97 in) wide.
• T4: The tumor can be of any size, but it is growing into the chest wall or skin. This category includes inflammatory breast cancer.

Factors that affect staging

Tumor size is just one of the factors that doctors consider when determining the stage of a person's breast cancer. Other factors include:

Lymph node status

When staging a person's breast cancer, doctors will determine whether it has spread to nearby lymph nodes. They do this by removing one or more of the lymph nodes in the armpit and examining them under a microscope. Doctors categorize lymph node status using the N value of the TNM system, where:

• NX means that the doctor was unable to assess the lymph node status
• N0 indicates that the doctor did not detect cancer in the nearby lymph nodes
• N1, N2, and N3 show that the cancer has spread to nearby lymph nodes. Higher values indicate the involvement of more lymph nodes

Metastasis

Metastasis is when cancer spreads from its original location in the breast to distant parts of the body, such as the liver, lungs, brain, or bones. The symptoms of metastatic breast cancer depend on which organs the cancer has spread to, and they can vary greatly. Doctors may use additional scans, tests, and exams to diagnose a person with metastatic breast cancer. Doctors categorize metastasis using the M value of the TNM system, where:

• MX means that the doctor was unable to assess metastasis
• MO indicates that the doctor did not detect any metastasis
• M1 means that the breast cancer has spread to other organs

Hormone receptor status

When staging breast cancers, doctors test the tumor cells for the presence of hormone receptors. The receptors are proteins that respond to the hormones estrogen and progesterone by telling the cancer cells to grow. Doctors describe breast cancer that has receptors for estrogen as being estrogen receptor-positive, or ER-positive. They refer to breast cancer that has receptors for progesterone as progesterone receptor-positive, or PR-positive. Breast cancers that have hormone receptors are far more likely to respond to hormone therapy.

HER2 status

HER2 status refers to whether breast cancer cells are producing too much of a protein called human epidermal growth factor receptor 2 (HER2). Doctors test for HER2 status by taking a sample of the cancer and sending it to a laboratory for analysis.

Doctors describe breast cancer with higher than normal levels of HER2 as being HER2-positive. HER2-positive cancers are typically more aggressive than other types of breast cancer, but they are also more likely to respond to targeted therapies.

Appearance of cancer cells

The appearance, or differentiation, of the cancer cells is another factor in cancer staging. Doctors grade cancer cells according to how similar they appear to noncancerous cells under a microscope.

Doctors classify cancer cells that are close to resembling healthy cells as being low grade or well differentiated. These cancers typically grow more slowly. High grade, or poorly differentiated, cancer cells appear very different than normal cells and tend to grow faster.

Breast cancer stages

After assessing the different characteristics of the breast cancer, doctors use the information to determine its overall stage from 0 to IV. Here is an overview of each breast cancer stage:

• Stage 0: This cancer is noninvasive and is only present inside the milk duct. This stage includes ductal carcinoma in situ (DCIS)
• Stage I: These are small tumors that either have not spread to the lymph nodes or are only affecting a small area of the sentinel lymph node
• Stage II: These are larger tumors that have spread to some nearby lymph nodes
• Stage III: These tumors are large or growing into surrounding tissues, such as breast skin, muscle, and lymph nodes
• Stage IV: These are tumors that started in the breast but have spread to other parts of the body

Treatment and outlook

When recommending treatment options for breast cancer, a doctor will take into account:

• The stage of breast cancer
• The person's age, general health, and personal preferences
• Whether the cancer is ER-positive, PR-positive, or HER2 positive
• The speed at which the cancer is growing

Treatment options can include:

• Surgery, which may involve removing the whole breast and any affected lymph nodes
• Radiation therapy
• Chemotherapy
• Hormone therapy
• Targeted therapy

Early detection and diagnosis of breast cancer can significantly improve a person's outlook. According to the ACS, the 5-year relative survival rate for localized breast cancer is 99%. This statistic means that people with this type of cancer are 99% as likely to survive for at least 5 years after diagnosis as those without the condition.

The 5-year relative survival rate is 85% for people with breast cancer that has spread into neighboring tissues and 27% for those whose cancer has spread to other organs. The overall 5-year relative survival rate for breast cancer is 90%. However, these figures are only estimates, and experts have based them on data from 2008–2014. Treatment for cancer is improving all the time, and each person's outlook is different.

Summary

Tumor size is an important factor when doctors are determining the stage of a person's breast cancer. However, doctors also take into account several other factors, including:

• Lymph node involvement
• The location of the cancer and whether it has spread
• Hormone receptor status
• HER2 protein status
• The appearance of cancer cells

A doctor will consider all of these factors in addition to the person's age, general health, and personal preferences when recommending treatment options. People with later-stage breast cancers may need more treatment than those whose cancer is at an early stage. Early diagnosis and treatment of breast cancer can significantly improve a person's outlook. However, everyone's experience of breast cancer is different.