What is Breast Cancer?

May 6, 2020

Understanding the different types of breast cancer.

Breast Cancer is the most common cancer in women across the globe, but discovering it, living with it and treating it can affect each patient very differently.

One reason for this variety of experiences is the numerous subtypes of the disease, each with its own standard of care. To find the best treatment plan, patients should discuss their individual cases with their physicians.

The good news is that today, there are 3.8 million breast cancer survivors living in the United States.


Breast cancer develops when cells in breast tissue change and divide in an uncontrolled manner. Most cancers start in the milk glands, called lobules, or in the ducts that connect the lobules to the nipple. In many cases, this forms a lump or tumor.

In 2019, it was expected that in women, 268,600 new cases of invasive breast cancer and 48,100 cases of ductal carci- noma in situ, stage 0 cancer confined to the ducts, would be diagnosed. About 2,670 cases of breast cancer were expected among men.


Some risk factors for breast cancer are inherited; others are modifiable.

Inherited risk factors include a family history of breast, ovarian, pancreatic or prostate cancer; a personal history of breast cancer; and mutations in the BRCA1 and/or BRCA2 genes. Modifiable risk factors in women include obesity, physical inactivity and alcohol consumption.

Since male breast cancer is rare, it has not yet been possible to verify whether the same risk factors apply for men.


The most common symptom of breast cancer is a painless lump that can be found either via imaging, such as a mam- mogram, when it is small, or by the patient when it grows big enough to be felt. If the cancer spreads to lymph nodes in the armpit, a lump or swelling can arise there. In other types of breast cancer, such as lobular and inflammatory, no lump forms.

Changes in the breast can also signal cancer. If the breast hurts or feels heavy, swells, turns red or develops thicker skin or if a nipple becomes scaly, retracts or leaks discharge, a doctor should be consulted.


Screening, such as a mammogram, often reveals breast cancer before symptoms develop. It’s also common for cancer to be found when a patient feels a lump. Most masses found in these ways are not cancerous, but if cancer is suspected, a doctor can use a needle to biopsy the lump and send the tissue for microscopic analysis.

If cancer is found, the doctor will determine the stage of the disease, from 0 to 4, to recommend a treatment regimen. In addition, the doctor will factor in the cancer’s subtype, including a consideration of the availability of effective treatments for that type. To determine the stage, the doctor will consider the cancer’s grade, based on its size and whether the disease has reached lymph nodes or other sites outside the breast. CT or PET scans can be used to find out if cancer has traveled to distant organs, such as the lungs or liver.

As part of staging, doctors should also use a genomic test on the tumor if breast cancer is fueled by hormones, does not make too much of the protein HER2 and hasn't spread to more than three lymph nodes. This test is used after surgery to predict how likely the cancer is to recur. One such test is Oncotype DX. If that test shows a recurrence score lower than 11, the patient may be able to safely skip chemotherapy and instead be treated with hormone-blocking medicine alone after surgery. Fitting into this group lowers the cancer stage to 1A.

Patients should make sure that doctors stage their cancers based on these guidelines, issued by the American Joint Committee on Cancer in its eighth edition, released in 2018.


Each of the three major molecular subtypes of breast cancer calls for a different strategy. The kind of breast tissue in which the cancer originated can also help direct treatment, as can the cancer’s stage. After receiving a breast cancer diagnosis, most women have their tumor tissue tested for genetic muta- tions, which can help guide treatment.

The three molecular subtypes are:

  • Hormone receptor-positive, HER2-negative breast cancer, the most common subtype, which is driven by hormones but not by the protein HER2.
  • HER2-positive breast cancer, which is driven by this protein. 4 Triple-negative breast cancer, which is not driven by hormones or HER2.

For ductal carcinoma in situ and other forms of early-stage breast cancer, surgery — either lumpectomy or mastectomy — is the primary treatment.

Patients who undergo mastectomy can consider breast reconstruction with a saline or silicone implant, tissue from another part of the body or a combination of both. It’s impor- tant for patients to make this decision prior to mastectomy and consult with doctors about the types of reconstruction available, as well as their pros and cons.

Women with stage 3 disease may receive chemotherapy before surgery to shrink the tumor. This presurgical regimen is known as neoadjuvant treatment. Patients with earlier- stage breast cancers typically receive chemotherapy after surgery, which is known as adjuvant treatment.

Chemotherapy can be very effective in HER2-positive breast cancers, where it is typically given in combination with Herceptin (trastuzumab), a drug that targets the protein HER2. Chemotherapy is less effective in triple-negative breast cancer, but an immunotherapy known as a checkpoint inhibitor can be used after surgery to treat some patients with this subtype when it is locally advanced or metastatic.

In hormone receptor-positive, HER2-negative breast cancer, patients typically get chemotherapy after surgery, followed by a prolonged course — five years or more — of drugs that block hormonal activity to help prevent recurrence. Patients with this subtype whose lymph nodes are not affect- ed by cancer and whose likelihood of recurrence is very low, based on Onctype DX test results, can skip chemotherapy.

For those with metastatic breast cancer that has spread to other parts of the body, such as the lungs, liver or bones, options (dependent on genomic test results) may include chemotherapy, hormonal treatments and targeted drugs such as the CDK4/6 inhibitors Ibrance (palbociclib), Afinitor (evero- limus) and Piqray (alepisib). Immunotherapy is approved to treat metastatic triple-negative breast cancer. Patients with metastatic disease might also choose an experimental drug, given as part of a clinical trial, as their first line of treatment. Depending on breast cancer’s subtype and stage, many patients will also need radiation therapy.


Chemotherapy’s side effects can include nausea, fatigue, hair loss, low red blood cell counts, diarrhea, fertility issues, menopause, mouth sores, changes in taste and smell, and numbness or tingling in the extremities.

Hormonal treatments can cause hot flashes, joint and muscle pain, fatigue, nausea and, in men, impotence.

Targeted drugs can cause diarrhea; nausea or vomiting; sleep problems; rash; mouth sores; problems with blood count; and cold symptoms.

Immunotherapy can trigger fatigue, diarrhea, constipation, vomiting, fever, joint pain, rash, urinary problems, endocrine gland disorders and pneumonia.


Many people never experience a recurrence after treatment for breast cancer, but the concern can linger for years. Patients should be on the lookout for longer-term side effects of treatment, such as heart problems or lymphedema, a pool- ing of liquid that causes swelling of limbs near areas where lymph nodes were removed. This common, incurable side effect can affect a patient’s appearance and interfere with daily life.

Women who have undergone surgery, with or without breast reconstruction, will need to adjust to the changes in their bodies. Younger women with hormone receptor- positive breast cancer will be put into medical menopause for at least five years after treatment. This can represent a major lifestyle change, and the drugs can cause side effects, including joint pain. Many patients experience sexual dys- function after treatment.

If the cancer has spread to distant parts of the body, patients will need treatment for the rest of their lives, and their life spans may be shortened.

All these changes can lead to emotional distress or even post-traumatic stress disorder in patients with breast cancer and their spouses.

Patients should consult their physicians about any changes that seem unusual and discuss side effects that arise from treatment, including those involving mental health, sexual dysfunction and pain.


Susan G. Komen Greater New York City (komennyc.org) offers information, support and other tools and resources to people affected by breast cancer. Don’t forget to review the resources listed online at curetoday.com/journey.