What is breast cancer?

Breast cancer is a medical condition in which there is uncontrolled growth of the breast cells. Globally, it is the most common cancer diagnosed in women, representing 1 in 4 of all cancers1. Fortunately, over the years, breast cancer survival rates have significantly increased thanks to technological advances in cancer discovery, management, and postoperative care.

Whether you are a patient or a carer, the first step in managing breast cancer is to understand what the disease is and how it occurs. Learning about the risk factors and causes of the cancer, as well as its treatment options, can also help in decision-making when it comes to cancer care.

Understanding breast anatomy

The breast of a mature woman contains mammary glands that perform the function of milk production. They are located on the front of the chest wall, rest on the major muscles of the chest, and are held in position by the ligaments.

Each breast consists of 15-20 lobes2 arranged in a circular pattern. The fat that surrounds the lobes gives the breast its size and shape. Each lobe is further divided into numerous lobules. The breast is affected by the following major hormones: prolactin, estrogen, and progesterone.

Causes of breast cancer

The causes of breast cancer are tightly linked to abnormal cell growth and unchecked proliferation.

There are an uncountable number of cells in the body of a human being. These cells are normally kept under very tight regulatory controls that determine when to multiply in number (proliferation), increase in size, or die. There are specific genes involved in the growth regulation of cells and if these genes become mutated, cells can lose the ability to regulate their growth, and this can lead to cancer.

Cancerous cells tend to proliferate without any control, leading to the formation of tumors. These continuously dividing cells acquire a long life span and grow unabated. They can also invade surrounding tissues locally or spread to other parts of the body.

Types of breast cancer

Breast cancer can first be classified according to the site of origin. This includes the lobular and ductal types of breast cancer.3


The milk-producing structures at the end of the breast ducts are called lobules, and this is where lobular breast cancer begins. In the United States, approximately 10% of all cases of breast cancer are of this kind.4


The much more prevalent kind of breast cancer is called ductal breast cancer, which arises from the breast ducts. If left untreated, it can spread from the ducts to nearby tissues.

Further classification of breast cancer types

Breast Cancer is further classified according to whether it is invasive or non-invasive (i.e. ‘In Situ’).  The non-invasive subtypes include Ductal Carcinoma in Situ (DCIS) and Lobular Carcinoma in Situ (LCIS).


Ductal Carcinoma in Situ (DCIS) is noninvasive and restricted to the inside of the breast ducts when the abnormal cells do not grow beyond the breast milk ducts
DCIS is graded based on the characteristics of the nuclei of the cells into low grade (grade I), intermediate grade (grade II), or high grade (grade III).
Low-grade DCIS cells resemble normal breast cells or atypical ductal hyperplasia. Grade II DCIS cells look less like unaffected but grow more than normal. High-grade DCIS cells have the highest risk of progressing to invasive carcinoma.


Breast lobules containing aberrant cells are the site of a non-invasive disease called Lobular Carcinoma in Situ (LCIS). In contrast to DCIS, LCIS is not regarded as a precancerous lesion and is typically not linked to a significant risk of invasive breast cancer. On the other hand, having LCIS can make a person more susceptible to breast cancer.
Although DCIS and LCIS are non-invasive, it is vital to remember that they are regarded as signs of invasive breast cancer. Early detection and routine tests are essential for detecting and treating them before they become invasive.

Invasive Subtypes of Breast Cancer

The invasive subtypes are further classified based on the expression of certain receptors. These receptors include estrogen receptors (ER), progesterone receptors (PR), and the HER2 protein.

Invasive Ductal Carcinoma (IDC) and (Invasive Lobular Carcinoma) ILC are the most common forms, and they can be categorized into ER+, PR+, and HER2+ based on cancer expression.

Another subtype of breast cancer is Triple-Negative Breast Cancer (TNBC), which is characterized by the absence of estrogen receptors, progesterone receptors, and the Her2 protein. TNBCs include metaplastic, medullary, inflammatory, and adenoid breast cancers.

Less common types of breast cancer

There are other less common invasive breast cancers like the inflammatory, medullary, carcinoid, and mucinous forms.

Stages of breast cancer

When you are diagnosed with breast cancer, the first step is to categorize the cancer according to its stage.

Breast cancer staging uses two different types of information: anatomic and prognostic. Anatomical staging assesses tumor size, whether the cancer has spread to the lymph nodes, and the presence or absence of distant metastasis, while prognostic staging includes tumor grade and biomarkers.

There are several stages of breast cancer, which can determine how advanced the disease is and how best to manage it.

Stage 0

Stage 0 describes a non-invasive breast cancer (such as DCIS or LCIS) where the abnormal cells are confined to the part of the breast in which they started growing and have not invaded nearby normal tissues.

Stage I

Stage I marks the early presence of invasive cancer where the cancer cells have broken through to the normal surrounding breast tissue. These are often small tumors still localized within the breast.

Stage II

Stage II signifies larger tumors or those with limited lymph node involvement.

Stage III

Stage III breast cancer refers to different degrees of tumor advancement. Sub-stages IIIA, IIIB, and IIIC involve an increase in tumor size, lymph node involvement, and potential invasion of adjacent structures.

Stage IV – Metastatic Breast Cancer (MBC)

Stage IV, or Metastatic Breast Cancer (MBC), indicates an advanced stage of the cancer whereby the tumor cells have moved to distant sites such as the liver, brain, lungs, and bones. In the US, nearly 30% of women who are diagnosed of early-stage cancer go on to develop metastatic breast cancer5.

Who gets breast cancer?

While anyone, regardless of sex, can develop breast cancer, it is much more common in women. The disease does not occur randomly either. Rather, it can affect individuals based on various risk factors, which are conditions that predispose one to get the disease. They can be grouped into modifiable and non-modifiable factors.

Modifiable risk factors include the following:

  • Alcohol consumption
  • Use of hormonal medication such as hormone replacement therapy (HRT) and oral contraceptive pills (OCP)
  • Radiation exposure
  • Sedentary lifestyle
  • Diethylstilbestrol exposure in utero
  • Type II diabetic mellitus
  • Obesity

Non-modifiable risk factors include:

  • Age: One of the most significant breast cancer risk factors is increasing age.  In the US, about two out of three invasive breast cancers are found in women aged 55 or older6, while in the EU, half of all estimated breast cancer cases occur in women aged 45-697
  • Family history: If there is a family history of breast cancer among your siblings, you’re at a high risk of developing the disease8. A family history of other cancers like prostate, lung, colon, and stomach cancer also increases risk
  • Genetic factors: Individuals with BRCA1 and BRCA2 gene mutations have a higher chance of developing breast cancer. In fact, BRCA1 and BRCA2 mutations account for approximately 5% of all cases of breast cancer9. Other gene mutations predisposing one to breast cancer include alterations of the STK11, MLH2, MLH1, and TP53 genes
  • Late menopause
  • Early menarche
  • Nulliparity
  • First pregnancy above the age of 30
  • Previous history of benign breast tumor

Signs and symptoms of breast cancer

Most breast cancers at early stages are asymptomatic and are discovered in the process of breast screening. Pain and discomfort are also not common with the disease, with only 5% of the patients with malignant breast disease experiencing pain10.

Common breast cancer symptoms include:

  • Having a lump in the breast
  • Change in overall breast size
  • Skin changes in the breast area
  • Nipple inversion
  • Ulceration
  • Bloody nipple discharge
  • Swelling of the lymph nodes under the armpit
  • Redness of the skin in the breast area

Understanding treatment options

Treatment of breast cancer is dependent on the stage of the disease. However, the following are the treatment options for breast cancer:

Medical therapies

Systematic therapies involve the use of medication given through the bloodstream to destroy cancer cells to keep them from growing and dividing. Examples include chemotherapy, hormone therapy, antibody-directed therapy, and target therapy.
Medical therapies are prescribed by medical oncologists and may be given before, during, or after surgery. They are also given on different schedules depending on the patient’s specific case11


Surgery focuses on local control of the cancer. There are several types of surgeries used in breast cancer:

  • A lumpectomy (or breast conserving surgery) removes cancerous breast tissue along with a small margin of normal tissue surrounding the lump.
  • Simple mastectomy removes the entire breast but excludes the removal of axillary lymph nodes.
  • Modified radical mastectomy also removes the entire breast along with most of the underarm lymph nodes but preserves the pectoralis major muscles.
  • Quadrantectomy involves the removal of approximately a quarter of the breast tissue, with 2-3 cm of healthy tissue surrounding the tumor.

Radiotherapy (Radiation)

Radiation is often used after surgery, as it can reduce recurrence of breast cancer12. However, for older women with specific cancer types, survival improvement isn’t proven.

Radiotherapy may be beneficial for larger tumors, invasive cases, or as palliative therapy in the advanced stages of the cancer.

Early diagnosis and prognosis

Breast cancer diagnosis

Early diagnosis is the key to the management of breast cancer, and this can be achieved by intermittent screening with your healthcare provider and self-breast examination.

The diagnosis is made using these triple-assessment methods:

  • Clinical examination: This involves history taking and physical examination, which helps to identify individual risk factors for the disease and assess for the possible complications.
  • Imaging: This investigation is done using mammography13, ultrasound, or Magnetic Resonance Imaging (MRI) with or without contrast.
  • Breast biopsy: Core biopsy, guided by imaging, is the preferred diagnostic approach for newly diagnosed breast cancers, which enables the physician to collect your breast tissue without surgical removal of the whole breast.

Breast cancer prognosis

The prognosis for breast cancer depends on cancer type, grade, and when it is detected. Factors such as the patient’s age and overall health also affect prognosis. Generally, the earlier breast cancer is detected and treated, the better the patient outcome. In the US, the five-year survival rate for women with breast cancer (that has not spread beyond the breast) is 99% and the five-year survival rate is 29% for women with Stage IV (metastatic) breast cancer.14


Breast cancer is a significant global health concern. The prognosis will be better with early detection through self-breast examination, screening for high-risk gene mutations, intermittent mammography screening, and early treatment to maximize appropriate patient care.

To achieve early detection, there is a need for regular awareness campaigns and health education. Understanding the risks of breast cancer can lead to better prevention against the disease, while awareness of treatment options can save lives. Promptly book an appointment with your healthcare provider if you notice any concerning symptoms regarding your breasts.


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  2. “Breast Anatomy.” National Cancer Institute: SEER Centre Training Modules https://training.seer.cancer.gov/breast/anatomy/
  3. “Types of Breast Cancer.” American Cancer Society. https://www.cancer.org/cancer/types/breast-cancer/about/types-of-breast-cancer.html
  4. Carter, Devon. “8 insights on lobular breast cancer.” MD Anderson Cancer Center, University of Texas. May 26, 2022. https://www.mdanderson.org/cancerwise/What-is-invasive-lobular-carcinoma-8-insights-on-lobular-breast-cancer.h00-159539745.html
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  10. Chalasani, Pavani, MD, MPH. Ed. John V Kiluk, MD, FACS. “Breast Cancer Clinical Presentation.” E-medicine, Medscape. Updated November 21, 2023. https://emedicine.medscape.com/article/1947145-clinical?form=fpf
  11. “Breast Cancer: Types of Treatment.” Cancer.net. October 2022. https://www.cancer.net/cancer-types/breast-cancer/types-treatment
  12. Early Breast Cancer Trialists’ Collaborative Group (EBCTCG). “Effect of radiotherapy after breast-conserving surgery on 10-year-recurrence and 15-year breast cancer death: meta-analysis of individual patient data for 10 801 women in 17 randomised trials.” The Lancet, 378 (9804), 1707-1716. November 12 ,2011. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3254252/
  13. “Breast Cancer Treatment Options.” Washington University Siteman Cancer Center. https://siteman.wustl.edu/treatment/cancer-types/breast-cancer/treatments/
  14. “Diagnosing your Breast Cancer.” Emory University: Winship Cancer Institute. https://winshipcancer.emory.edu/patient-care/cancer-types/breast-cancer.html
  15. “Breast Cancer.” Yale Medicine. https://www.yalemedicine.org/conditions/breast-cancer
  16. Dafni, U., Tsourti, Z., & Alatsathianos, I. “Breast Cancer Statistics in the European Union: Incidence and Survival across European Countries.” Breast care (Basel, Switzerland), 14(6), 344–353. 2019. https://doi.org/10.1159/000503219


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