Breast Cancer, Its Etiology and Pathophysiology

Definition

Breast cancer is a serious health condition, characterized by the “uncontrolled growth of malignant cells in the mammary epithelial tissue” (Lukong, 2017, p. 64). It is one of the most common health causes of death in women and the most popular type of cancer diagnosed in women. There are a variety of risk factors associated with the development of breast cancer, including age, gender, and family history.

Although there are distinctive diagnostic and treatment procedures for breast cancer, treatment success depends largely on the stage of the disease and its characteristics. Thus, breast cancer poses a significant risk to the health and well-being of women worldwide. This report will aim to provide comprehensive information on breast cancer, including statistical data, risk factors, development, and symptoms, as well as contemporary diagnostic and treatment measures used for breast cancer.

Morbidity and Mortality

Breast cancer is one of the deadliest diseases threatening women all over the globe. According to Senkus et al. (2013), “In 2008, the estimated age-adjusted annual incidence of breast cancer in Europe (40 countries) was 88.4/100 000 and the mortality 24.3/100 000” (p. 7). Thus, almost one-quarter of all breast cancer cases in 2008 were lethal. The burden of disease did not reduce over time. In 2012, over 1.7 million cases of breast cancer were diagnosed worldwide, while the number of people who died from breast cancer reached 521,900 (Pearis, Choi, Stewart, & Sateia, 2017).

Although the distribution of breast cancer is relatively even across different parts of the world, women in developing countries face a higher risk of dying from breast cancer. According to Pearis et al. (2017), 62% of all cancer deaths occurred in developing countries.

Moreover, the rate of 5-year survival for women living in low-income countries is two times lower (below 40%) than for those living in high-income countries (80%), which stresses the burden of the disease in developing countries (Shah, Rosso, & Nathanson, 2014). In the United States, breast cancer is also common: as noted by Shah et al. (2014), an American woman’s lifetime risk of developing breast cancer is 12.4%. The disparities that exist between developed and developing countries in terms of cancer mortality are mostly due to screening and diagnostics; research proves that an early diagnosis could help to improve the survival rate (Shah et al., 2014).

Etiology and Risk Factors

The etiology of breast cancer remains relatively undefined, although a number of efforts were undertaken to define the causes of the condition. Most of the researchers suggest that hormonal changes, particularly in estrogen levels, are linked to breast cancer (Senkus et al., 2013). However, the research found a variety of risk factors that are significantly linked to the development of the disease.

First of all, according to Shah et al. (2014), age is a major risk factor, and the risk of developing breast cancer increases with age. For instance, whereas a lifetime risk of breast cancer for an American woman is 1 in 8, it is 1 in 202 for women under 39 years of age, 1 in 26 for women aged 40 to 59 years, and 1 in 28 for women between 60 and 69 years of age (Shah et al., 2014). Therefore, age is among the key factors affecting the onset and development of breast cancer.

Hormone imbalance is also a significant risk factor. As noted by Pearis et al. (2017), high endogenous levels of estrogen are associated with an increased risk of developing breast cancer in women before and after menopause. Moreover, in post-menopausal women, continuous use of HRT contributes to the risk of breast cancer Paris et al., 2017).

Reproductive history is considered to be associated with the risk of breast cancer. Early age of first menstruation, late age of first birth (over 30 y.o.), and late menopause (over 55 y.o.) were found to increase the lifetime risk of breast cancer (Pearis et al., 2017).

Personal and family history of cancer also contributes to the increased risk of breast cancer. For instance, Shah et al. (2014) suggest that previous cases of breast cancer in female relatives are a major risk factor for the development of the disease, while a personal history of breast cancer contributes to the risk of recurrent condition. Moreover, Pearis et al. (2017) state that the personal history of other cancers, such as ovarian or endometrial cancer, also increases the risk of breast cancer.

Overall, women with a history of breast cancer in the family, who gave birth at a late age and are now in the post-menopausal stage of life are at the highest risk of developing breast cancer.

Pathophysiology

Breast cancer is characterized by the uncontrolled growth of breast cells. It is unclear what triggers the uncontrolled growth of cells and their transition into carcinoma. However, certain patterns exist in the pathophysiology of breast cancer that allowed researchers to track its source and developmental pattern.

Most commonly, the malignant tumor develops in the upper outer quadrant or the center of the breast (VanMeter & Hubert, 2013). The cells of the ductal epithelium that outline breast ducts are usually the source of the cell change. In this case, malignant cells infiltrate the nearby tissues and can cause the tumor to adhere to the chest muscle, thus becoming fixed (VanMeter & Hubert, 2013).

Malignant cells can also spread to lymph nodes, especially if they are located in the upper outer quadrant of the breast. If a lymph node becomes affected, cancer cells can disseminate to other organs, producing metastases to the brain, lungs, and liver (VanMeter & Hubert, 2013). The success of treatment largely depends on the presence of metastases, which is why it is crucial for women to prevent the tumor from producing metastases by ensuring early diagnosis of the disease (Giuliano et al., 2017).

Therefore, two key types of breast cancer can be outlined: invasive and in situ. In situ breast cancer is localized within the breast lobules and/or ducts and does not affect lymph nodes or other organs (Ward et al., 2015). Invasive breast cancer, on the other hand, spreads to other tissues and has the capacity to produce metastases into other organs.

Researchers also use gene profiling to identify subtypes of breast cancer. Gene profiling can be used to divide breast cancer into four subtypes: basal-like, HER2 (human epidermal growth factor receptor 2)-positive, luminal A, and luminal B (Lukong, 2017). These types differ by their reception of estrogen and progesterone. For instance, basal-like breast cancer tumors are normally ER-, PR-, and HER-negative tumors, which can make them triple-negative (Lukong, 2017). Different types of breast cancer differ by patient and treatment outcomes, with triple-negative tumors being the most dangerous.

Signs and Symptoms

The main symptom of breast cancer is the presence of a single nodule, which is usually small and hard, allowing it to be easily palpated (VanMeter & Hubert, 2013). The nodule can be easily moved during the early stages; after the tumor grows into other tissues and the chest muscle, it becomes fixed (VanMeter & Hubert, 2013). Another typical sign of the condition is nipple discharge, which can be bloody or serous. Pain is not usually present in the first stages of breast cancer (VanMeter & Hubert, 2013). However, other symptoms might be visible if cancer has already metastasized to other organs.

Diagnostics

Diagnostic imaging is the key procedure used in the primary detection of breast cancer. Mammography, magnetic resonance imaging (MRI), and ultrasound are commonly used to identify the size and location of the nodule (Shah et al., 2014). Mammography and MRI are also used for regular screening, which is recommended for all women, especially for those with a family history of breast cancer (Senkus et al., 2013).

If the presence of a nodule is confirmed, further diagnostic procedures are required. For instance, it is crucial to determine the state of regional lymph nodes, which is normally done using ultrasound (Senkus et al., 2013). A pathological examination of the primary tumor is used to differentiate between a benign and a malign tumor. For breast cancer, a biopsy obtained manually or with ultrasound guidance usually serves the needs of pathological diagnosis.

The sample obtained through biopsy should be examined for “histological type, grade, immunohistochemical (IHC) evaluation of estrogen receptor (ER) status using a standardized assessment methodology (e.g., Allred or H-score)” (Senkus et al., 2013, p. 8). For invasive breast cancer, IHC assessment of the PgR and HER2 receptor expression is also required (Senkus et al. 2013). After obtaining sufficient diagnostic information, the oncologist can determine the stage and type of breast cancer, which allows planning treatment.

Treatment

According to Shah et al. (2014), the presence of malignant changes in the axillary lymph nodes often determines medical decision-making and treatment planning following lumpectomy or mastectomy. If lumpectomy has already taken place and the lymph nodes are unaffected (negative), radiation therapy to breast followed by chemotherapy is usually chosen, although partial breast irradiation is used in some patients (Shah et al., 2014).

However, if four axillary nodes are positive after lumpectomy, radiation therapy to internal mammary nodes is advised (Shah et al., 2014). The patient can avoid radiation therapy completely if the had a total mastectomy with negative axillary nodes and tumor size less then or at 5 cm (Shah et al., 2014). Overall, surgery, radiotherapy, and chemotherapy are the main three methods used in the treatment of breast cancer, either separately or together.

Conclusion: Outlook and Complications

Overall, breast cancer is a prominent health issue that can severely affect the health and well-being of women. The most common complications of breast cancer are those associated with metastases to other tissues and organs. For example, breast cancer might lead to lung, brain, or liver cancer, which severely impairs the patient’s quality of life and prognosis. However, even in case of timely diagnosis and lack of metastases, breast cancer can result in treatment complications. For instance, mastectomy or lumpectomy can lead to scarring, swelling, and wound infection, as well as psychological symptoms, including depression and impaired self-perception.

Chemotherapy often leads to hair loss, nausea, weight loss, and fatigue, whereas radiation therapy can cause lymphedema, burns, and heart disease. Researching new treatment methods can improve patient outcomes and help to avoid complications resulting from breast cancer or its treatment. Moreover, research on the etiology and pathophysiology of the disease could help to understand its development, thus enabling women all over the world to protect themselves from breast cancer.

References

Giuliano, A. E., Connolly, J. L., Edge, S. B., Mittendorf, E. A., Rugo, H. S., Solin, L. J., &… Hortobagyi, G. N. (2017). Breast cancer-major changes in the American joint committee on cancer eighth edition cancer staging manual. CA: A Cancer Journal for Clinicians, 67(4), 290-303.

Lukong, K. E. (2017). Understanding breast cancer – The long and winding road. BBA Clinical, 7(1), 64–77.

Pearis, K. S., Choi, Y., Stewart, R. W., & Sateia, H. F. (2017). Screening for breast cancer. Seminars in Oncology, 44(2), 60-72.

Senkus, E., Kyriakides, S., Penault-Llorca, F., Poortmans, P., Thompson, A., Zackrisson, S., & Cardoso, F. (2013). Primary breast cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Annals of Oncology, 24(6), 7-23.

Shah, R., Rosso, K., & Nathanson, S. D. (2014). Pathogenesis, prevention, diagnosis and treatment of breast cancer. World Journal of Clinical Oncology, 5(3), 283-298.

VanMeter, K. C., & Hubert, R. J. (2013). Gould’s pathophysiology for the health professions. Cambridge, England: Elsevier Health Sciences.

Ward, E. M., DeSantis, C. E., Lin, C. C., Kramer, J. L., Jemal, A., Kohler, B.,… Gansler, T. (2015). Cancer statistics: Breast cancer in situ. CA: A Cancer Journal for Clinicians, 65(1), 481-495.