Medicina de precisão do Hospital Israelita Albert Einstein

Breast Cancer: All about it

câncer de mama
câncer de mama

In the last 20 years, the total number of patients diagnosed with cancer has almost doubled. Today, over 19 million people have been diagnosed, and this number is expected to continue to increase in the coming years.

Recently, according to data from the International Agency for Research on Cancer (IARC), breast cancer has become the most commonly diagnosed form of cancer in the world, surpassing lung cancer.

Although breast cancer is extremely lethal, there are treatments available. Early diagnosis and the adoption of techniques for regression of stages can help the recovery process. Want to know more about this disease? Follow the content!

What is breast cancer?

Breast cancer is a type of cancer that starts in the breast. Like other types of cancer, breast cancer results from uncontrolled growth of cells that usually form a malignant tumor.

This tumor can be observed through X-ray examination and can often be felt through touch as a lump.

There are other types of non-malignant breast lumps that do not categorize as breast cancer. However, although benign lumps are not fatal, they can increase the risk of developing cancer, so they should also be checked.

Main risk factors

Breast cancer risk factors may be related to the environment, such as lifestyle, diet, or medication use, but they may also be factors such as age, sex, or genetics. Although risk factors can increase the chance of developing cancer, it does not mean that the person will actually develop the disease.

Among the main lifestyle-related risk factors are:

  • Alcohol consumption;
  • Obesity or overweight, especially in women after menopause;
  • Not being physically active;
  • Not breastfeeding;
  • Use of hormonal contraceptives;
  • Hormonal therapy after menopause;
  • Breast implants.

Other risk factors related to independent characteristics of lifestyle are:

Age

The risk of developing breast cancer progressively increases from age 35. Women over 55 years of age have a higher risk due to exposure to different risk factors throughout their lives.

Being a woman

Although men can also develop breast cancer, it represents only about 1% of cases. The risk is much higher for women.

Genetics and breast cancer

About 5 to 10% of breast cancer cases are hereditary, meaning they are germline mutations that are passed down from parents to children. Among the main genes related to an increased risk of developing breast cancer are:

BRCA1 and BRCA2: These genes are associated with the DNA repair system. Changes in these genes can disrupt their function and lead to abnormal cell growth, which can cause cancer.

On average, a woman with a pathogenic mutation in the BRCA1 or BRCA2 gene has about a 70% chance of developing breast cancer by age 80, as well as a higher probability of being diagnosed young.

This knowledge is due to studies in the GWAS format, which allows the association of genes with pathologies presented in a common phenotype, expanding the field of oncology.

There are more than 1000 known mutations of the BRCA genes. Mutations in these genes are also associated with a higher risk of developing ovarian cancer.

Other genes involved in breast cancer pathogenesis:

  • TP53: Helps to stop the growth of cells with damaged DNA;
  • PALB2: Produces a protein that interacts with the protein produced by the BRCA2 gene;
  • STK11: Changes in this gene can cause Peutz-Jeghers syndrome;
  • PTEN: Helps regulate cell growth. Changes in this gene can cause a rare disorder that increases the risk of developing benign tumors;
  • CHEK2: DNA repair system;
  • ATM: DNA repair system. Inheriting 2 abnormal copies of this gene causes ataxia-telangiectasia disease;
  • CDH1: Changes in this gene are associated with the development of a rare type of stomach cancer. Women with mutations in this gene have an increased risk of invasive lobular breast cancer.

Breast cancer symptoms

The main symptom related to breast cancer is the appearance of a lump in the breast. However, some types of cancer do not present the growth of lumps, so it is important to know the other symptoms related to the disease and be aware if possible changes arise.

Some symptoms related to breast cancer are:

• Hard and fixed lump or with increased size;

• Nipple discharge outside of pregnancy or postpartum;

• Eczematous lesion;

• Progressive increase in the breast size;

• Skin with an orange peel appearance;

• Skin retraction of the breast;

• Change in nipple shape or color.

Illustration of breast cancer signs

Types of breast cancer

There are different types of breast cancer, which can be determined according to the specific cell initially affected. The neoplasm can start:

In the ducts that transport milk to the nipple

In the lobes of the breast, the gland responsible for milk production

In other cells and tissues of the breast, such as sarcomas and lymphomas.

Learn more in the text: Lymphoma: Understanding the relationship with the immune system.

Breast cancer can also be categorized by whether or not it spreads to other parts of the breast or body.

Non-invasive cancers are also called in situ breast cancer. In situ means “in the original site”, so these are the types of cancers that do not spread to other regions of the breast beyond where they started. Also, because it is non-invasive, it does not spread to other parts of the body (metastasis). There are two types of in situ breast cancer:

Ductal Carcinoma In Situ (DCIS)

The most common type of breast cancer is carcinomas, tumors that start in epithelial cells. Ductal carcinoma in situ is a cancer that begins in a milk duct but does not spread to nearby breast tissue.

However, the possibility of DCIS transforming into an invasive cancer is not ruled out. According to the American Cancer Society, about 1 in 5 new breast cancers will be DCIS. The chance of recovery for patients diagnosed at this stage is almost complete.

Lobular Carcinoma In Situ (LCIS)

It is a cancer that starts in the cells of the breast lobes but does not spread to nearby breast tissue. LCIS is highly treatable and rarely becomes invasive cancer.

The term invasive breast cancer is used to describe any type that spreads through the surrounding breast tissue. Invasive breast cancer is the most frequent among those diagnosed. Among them, there are different types, with the most common being invasive ductal carcinoma and invasive lobular carcinoma.

Invasive breast cancer

This is the type of cancer that is present in adjacent breast tissue because it has already spread to other regions different from the original one. In this scenario, the most common types of invasive breast cancer are:

Invasive Ductal Carcinoma (IDC)

This is the most common type of breast cancer, accounting for about 80% of all invasive breast cancer cases. This cancer starts in the cells that line a milk duct and invades nearby breast tissue. When it comes into contact with the lymphatic system or bloodstream, malignant cells can spread to other parts of the body.

Invasive Lobular Carcinoma (ILC)

This type accounts for about 10% of invasive breast cancer cases. ILC begins in the lobules, the milk-producing glands, and can spread to other tissues and/or other parts of the body. About 1 in 5 patients with ILC develop cancer in both breasts. This type of cancer presents greater difficulty in detection through physical or imaging exams compared to others.

Inflammatory breast cancer

This is a more aggressive and fast-growing type of cancer, in which malignant cells invade the skin and lymph vessels of the breast. Typically, it does not produce a tumor or nodules, but when cancer cells block lymph vessels, symptoms begin to appear. Inflammatory breast cancer typically grows rapidly and requires aggressive treatment.

Triple-negative breast cancer

This is an aggressive type of breast cancer in which treatments such as hormone therapy and drugs that target estrogen, progesterone, and HER-2 are ineffective. This is because this tumor does not have the three main receptors known for accelerated cell growth: type 2 hormonal epidermal growth factor receptor (HER-2), estrogen receptors, or progesterone receptors.

Less common types of breast cancer

In addition to the types mentioned above, breast cancer can develop in less common ways, as in the following cases:

Paget’s disease

This type of cancer is less common than those mentioned above, accounting for about 1-3% of cases. It starts in the breast ducts and spreads to the nipple epithelium and then to the areola.

Angiosarcoma

Also known as breast sarcomas, they are even rarer, representing about 1% of breast cancer cases. This type of cancer begins in the cells that line blood or lymphatic vessels, and may also involve breast tissue or skin.

Phyllodes tumor

This rare type of breast tumor is usually benign, but in some cases it can become cancerous. Unlike other types that start in the ducts or lobules, it develops in the breast’s connective tissue.

Diagnosis

Identifying and starting treatment early can prevent death from cancer. This is because early identification can prevent cancer from spreading to other breast tissue or other parts of the body, making it easier to control. Therefore, it is important to undergo frequent screening tests.

Screening refers to tests performed preventively to identify possible changes in the patient’s health. Regarding screening, exams can identify cancers in the early stages of development, even without the appearance of palpable or visible symptoms.

Main screening tests for breast cancer

Mammography

In this exam, an X-ray of the breasts is taken, which, when performed regularly, can help detect breast cancer at an early stage. Mammography is considered the standard exam for cancer diagnosis.

The National Cancer Institute (INCA) recommends that mammography be performed once every 2 years for women aged 50 to 69.

The recommended age range is related to the occurrence of false positive or negative diagnoses for younger or older women.

This is because women under 50 have denser breast tissue, meaning they have more glandular tissue and less fat, which reduces the accuracy of the exam in identifying cancer lesions.

In women over 70 years old, the risk is to identify a cancer that would not evolve to the point of harming the woman’s health, thereby exposing her to unnecessary risks related to the treatment of the disease.

Breast self-examination

The strategy of breast self-examination was developed with the aim of guiding women to identify changes related to breast cancer through a specific breast palpation technique that should be performed monthly.

However, studies concluded in the late 1990s showed that the technique did not reduce women’s mortality, who continued to discover cancer occasionally.

Currently, the guidance is known as breast awareness, which means being aware and attentive to breast health.

The new strategy also aims to guide women to identify changes in the breasts, but without a specific technique or standardized method it may not offer the same benefits of a clinical evaluation.

In other words, the patient is encouraged to palpate the breasts whenever they feel comfortable to do so, observe changes in the shape, texture, and color of the breasts, and seek a health professional to report any changes.

Biomarker test

This test is used to find out if cancer cells have certain receptors. Breast cells have biomarkers that bind to the hormones estrogen and progesterone.

Another type of biomarker is the hormonal epidermal growth factor or HER2, which is found on the surface of all breast cancer cells. These receptors are necessary for cells to grow and divide.

Genetic test for breast cancer

Some inherited genetic changes from parents can increase the risk of breast cancer. Therefore, genetic testing can be performed to find these changes in patients’ DNA.

It is mainly recommended for people with a family history of cancer, who have been diagnosed with another type of cancer such as ovarian cancer or for cases of triple-negative breast cancer.

For this test, genetic sequencing of the main genes related to the highest risk of developing cancer mentioned above is performed, mainly the BRCA genes.

Seeking a trained professional in genetic counseling is important to understand the probabilities of developing the disease and receive guidance on possible steps to be taken.

Treatments

The treatment for breast cancer mainly depends on the stage of the disease. The stage of cancer indicates the size of the tumor and whether cancer cells are restricted to the site of origin or not. The treatments typically performed in each stage are:

Stage 0

The cancer is confined to the site of origin of the first abnormal cells. This stage requires treatment, usually surgery and/or radiotherapy. Chemotherapy, in most cases, is not part of the treatment for early stages of cancer.

Stage 1

The cancer is confined to the site of origin of the first abnormal cells, but the cancer is already evident. This stage is divided into 1A and 1B and differs in tumor size and evidence of cancer in lymph nodes.

Stage 1 is also highly treatable and usually requires surgery and/or radiotherapy. Like stage 0, patients in stage 1 also do not usually undergo chemotherapy. However, hormonal therapy is offered for some types of cancer.

Stage 2

The cancer is getting larger, but it is still confined to the breast or has only spread to nearby lymph nodes. This stage is divided into 2A and 2B and differs in tumor size and whether cancer is present in lymph nodes. In this stage, chemotherapy is performed, followed by surgery and radiotherapy.

Stage 3

The cancer has spread beyond the region of origin of the tumor and may have invaded nearby lymph nodes and muscles, but not to distant organs. This stage is divided into 3A, 3B, and 3C and differs in tumor size and whether cancer is present in lymph nodes and surrounding tissues.

Treatment options at this stage consist of mastectomy and radiation, local treatment, and hormonal or chemotherapy.

Stage 4

The cancer has spread to other areas of the body (metastasis), such as the lungs, bones, brain, or other organs. Although cancer at this stage is not curable, there are treatment alternatives capable of increasing

References

American Cancer Society

INCA: Instituto Nacional do Câncer

Harbeck, N., Penault-Llorca, F., Cortes, J. et al. Breast Cancer. Nat Rev Dis Primers 5, 66 (2019). https://doi.org/10.1038/s41572-019-0111-2

WHO: World Heath Organization : Breast Cancer

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