Breast Cancer: What you need to know

Cancer is a collective term referring to many different diseases. Simply put, cancer is uncontrolled cell growth, which can lead to tumor formation. A non-invasive tumor (in situ cancer) remains within the tissue where it originated. A malignant tumor (invasive cancer) has potential to spread to neighboring tissues and can form new tumors (metastases) elsewhere in the body. Tumors become dangerous when vital organ function is threatened by the overgrowth of cancer cells1.


Breast cancer is expected to affect 1 in 8 women, making it the most common cancer in women, after skin cancer2. This article discusses: diagnosis, treatment, taking proactive steps, and finding support.



In 2019, the US reported 3.8 million breast cancer patients and survivors.

Although breast cancer incidence is slightly higher in white women, breast cancer-related mortality is almost 50% higher in black women3. More than half of breast cancer patients are diagnosed at an early stage; however, men are slightly more likely to be diagnosed at a later stage compared to women.  As men make up just 1% percent of all breast cancer patients, there is still much to be learned about male breast cancer2,4.



Created for the National Cancer Institute,

Breast cancer can be diagnosed by imaging and histology (pathologic review). Imaging techniques help to visualize cancerous growths. Mammography, the most routine imaging technique used in breast cancer diagnostics, uses x-ray imaging5. There are some limitations, such as mild discomfort, very low radiation exposure, and a false positive rate. Ultrasound is often used to further define mammogram findings.  Additional imaging techniques (such as MRI breasts) are sometimes used; however, these techniques are expensive and still lack specificity (can have false positive findings).

Histology is the study of cells under the microscope6. Healthy cells usually look very uniform, but cancerous cells vary in shape and size. This is one way that they can be identified under the microscope; however, some non-cancerous diseases can cause cells to ‘look suspicious’. In such cases, cells can be stained for breast cancer-specific biomarkers to clarify the disease diagnosis7.

Cancer staging:

Once a diagnosis has been made, doctors must determine how far the cancer has progressed. The American Joint Committee on Cancer (AJCC) classifies tumors using the Tumor Node Metastasis (TNM) model. Specifically, this classification describes: the tumor size, the number of lymph nodes involved, and whether the tumor has metastasized. The details of the TNM model can be summarized using a 5-stage system, where stage 0 is in situ (non-invasive) cancer, and stages 1 through 4 are progressive extents of invasive cancer. Cancer staging helps doctors determine how much risk the cancer poses to a patient, and how it should be treated8–10.



When breast cancer is diagnosed at an early stage, surgery can be performed to remove the cancerous tissue. A lumpectomy is surgery that only removes the tumor, while a mastectomy removes the entire breast. The choice of surgery depends on the breast size, tumor size and location, and other factors. Lymph nodes are often also removed to determine the cancer stage, or if they are already known to contain cancer cells11.


Lumpectomy, accompanied by radiation treatment, has become standard practice, as it reduces the risk of local cancer recurrence in both in situ and invasive cancer12.

Radiotherapy uses high doses of radiation to destroy cancer cells by damaging their genetic material. Cancer cells are limited in their ability to repair damage. This makes them more susceptible to radiation than healthy cells, which are better at repairing damage. Nonetheless, healthy cells and tissues within and surrounding the breast can be damaged by radiation. Accordingly, radiation treatments are carefully planned to spare and protect healthy tissue13,14.


Chemotherapy can be used to shrink tumors prior to surgery (neoadjuvant), to prevent recurrence after surgery (adjuvant), or to treat advanced (metastatic) breast cancer15–17. Chemotherapy is a systemic medication that damages the genetic machinery needed for cell division, making it efficient in eliminating rapidly growing cells (such as cancer cells). Healthy cells with a high growth rate, such as those found in hair follicles and the digestive system, are also affected by chemotherapy, and this leads to the well-known side effects of hair loss and nausea18.


Targeted therapy, often used in combination with chemotherapy, focuses on specific molecules that stimulate growth or survival in cancer cells19. Hormone therapy is used in specific breast cancers where growth is stimulated by the hormones estrogen or progesterone. When cells are prevented from interacting with these hormones, hormone-induced growth is inhibited20. Some therapies are targeted at proteins that are associated with the growth of certain breast cancers. Tumors with high expression of HER2 can be treated with anti-HER2 therapies, which inhibit the function of this protein21. The choice of targeted therapy is dependent on the molecule that a particular type of breast cancer ‘responds to’. This is an important step towards personalized medicine: profiling a specific patient’s cancer and treating it accordingly to maximize treatment efficacy22.


Interestingly, when a tumor first forms, the immune system recognizes this as a strange event and tries to oppose tumor formation. Some cancer cells develop mechanisms that make them undetectable to immune cells. This is called immune tolerance. Immunotherapy aims to re-establish the immune system’s ability to detect cancer cells and combat immune tolerance23,24.


Altogether, breast cancer treatment is a multidisciplinary approach that benefits from the combination of different therapies. Besides increasing treatment efficacy, combination therapy can allow for the use of lower doses, which reduces adverse effects and delays drug resistance25.


What you should do:

Women are encouraged to take a proactive approach to their health, especially as it relates to breast cancer. Primary breast cancer prevention is the avoidance of known risk factors. Secondary prevention is early detection26. The American Cancer Society recommends that women can choose mammogram screening starting at age 40, but that all women should start annual mammogram screening by age 45.  Also, adult women should consider performing monthly self-exams. Forty percent of breast cancers are detected by the patients themselves27,28.

When breast cancer is familial, or has an early age of onset, genetic testing is often advised. If genetic testing suggests a high possibility for breast cancer development, preventative treatments, such as medications or risk-reducing mastectomy, are available.  Also, enhanced screening for cancer is considered for some genetic testing results.  In all cases, the psychological effects of genetic testing should be taken into account. The cancer risk should be well examined in order to avoid unnecessary interventions29.

Finding support:

Breast cancer treatment extends well beyond the confines of the doctor’s office. Support groups, hosted by mental/medical healthcare professionals or cancer survivors, can offer shared experiences/education and can provide a sense of community and comradery30. Psychoeducational support groups provide patients and their families with the knowledge and psychological tools they need to move forward in a holistic manner31.

Cancer, of any kind, is a difficult road to travel; access to the right people and the right information can provide fuel for the journey.



About the Author

Carol Tweed, MD joined Maryland Oncology Hematology in our Annapolis division October 2020. Dr. Carol Tweed attended Duke University, where she was inducted into Phi Beta Kappa. She graduated summa cum laude with a degree in Biology, and a concentration in molecular biology. She received her medical degree from Washington University in St. Louis, where she was elected to Alpha Omega Alpha. She then completed her Internal Medicine Residency and Hematology/Oncology Fellowship at the University of Pennsylvania.

From 2006-2012, Dr. Tweed was an Assistant Professor on faculty at the University of Pennsylvania’s Abramson Cancer Center. During this time, she practiced as a breast oncology specialist and enthusiastically educated medical students, residents, and fellows.

In 2012, she moved to Annapolis, MD, and joined AAMC Oncology & Hematology, before joining Maryland Oncology Hematology in October 2020. Dr. Tweed passionately cares for patients with a broad range of hematologic and oncologic disorders. Her work as a breast medical oncology expert continues.  She is a regional speaker on the topics of breast cancer and cancer genomics. She is co-founder and co-director of the Maryland Breast Cancer Consortium.

Dr. Tweed is an active clinical researcher; she has served as principal investigator on numerous national and international clinical trials. She also is an Instructor of Medicine/preceptor for Johns Hopkins School of Medicine, educating medical students.

Dr. Tweed is board certified in Hematology and Medical Oncology.



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