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Types Of Breast Cancer

Overview

Cancer is defined as the uncontrolled growth of abnormal cells<a href="#accordion">[1]</a>. These cancer cells can invade nearby organs or tissues. Cancer that occurs in the breast tissues is called breast cancer. 
&nbsp;

In 2020, there were a total of 2.3 million new cases and 685,000 deaths from breast cancer, making it the most common cancer across the world<a href="#accordion">[2]</a>. Unfortunately, these numbers are only expected to increase with experts predicting over 3 million new cases and 1 million deaths in 2040<a href="#accordion">[2]</a>.

Breast cancer is the most common cancer among women and the leading cause of cancer-related deaths in women<a href="#accordion">[3]</a>. Its incidence continues to increase across the world, with high income countries reporting the highest incidence<a href="#accordion">[4]</a>. This is mostly attributed to a sedentary lifestyle and Western diets, which are fast becoming a common trend worldwide. However, despite the higher incidence rates, the mortality rate is much lower in high income countries, compared to low and middle-income countries<a href="#accordion">[5]</a>. Better screening programs and advanced treatment facilities are believed to contribute to the higher survival rates in these high-income nations. 
&nbsp;

Male breast cancer accounts for less than 1% of cases<a href="#accordion">[7]</a>. While it is a rare occurrence, its incidence has shown a gradual rise<a href="#accordion">[8]</a>. Moreover, male breast cancer has lower survival rates due to advanced stage presentation, higher age at diagnosis, and limited information on its management<a href="#accordion">[8]</a>.&nbsp;&nbsp;&nbsp;&nbsp;

In Asia, Pakistan has the highest rate of breast cancer, with 1 in 9 women receiving a breast cancer diagnosis<a href="#accordion">[6]</a>. More than 34,000 new cases of breast cancer were reported in the country in 2018; these numbers are expected to rise further in the coming years<a href="#accordion">[5][6]</a>. The lack of awareness, religious misconceptions, fear of surgery, cultural norms, stigmatization, and hesitancy to go to male doctors all serve as barriers to screening and treatment<a href="#accordion">[5]</a>. Thus, leading to a delay in diagnosis and treatment, and contributing to the high mortality rate. 
&nbsp;

Depending on where the cancer originates, how much it has grown or spread, and how it behaves, breast cancer can be classified into various types<a href="#accordion">[9][11]</a>. 
&nbsp;

The first major classification is into in-situ and invasive carcinoma. 
&nbsp;

<h5>Non-Invasive Breast Cancer</h5>

In-situ or non-invasive breast cancer refers to cancer that has not spread beyond its point of origin. They are also called precancers. The two main types of non-invasive breast cancer are: 
&nbsp;

<ul>
	<li>Ductal Carcinoma In-Situ (DCIS) - This accounts for 16% of all breast cancer cases. The cancer originates in the milk ducts but does not spread outside. It is a precursor to invasive breast cancer. Therefore, treatment is required for DCIS. Doctors typically advise breast-conserving surgery which involves surgical removal of the tumor and a small amount of surrounding breast tissue<a href="#accordion">[10]</a>. It is usually followed by radiation therapy. In the case of a large DCIS, a simple mastectomy may be needed<a href="#accordion">[10]</a>. Moreover, tamoxifen or an aromatase inhibitor is prescribed if the cancer is hormone-receptor-positive. 
	&nbsp;</li>
	<li>Lobular Carcinoma In Situ (LCIS) - As the name implies, this non-invasive breast cancer originates in the lobules but does not spread beyond. However, it is not a true breast cancer, but rather a benign condition. 
	&nbsp;</li>
</ul>

<h5>Invasive Breast Cancer</h5>

This refers to breast cancer that grows outside of the normal ducts and lobules into the breast connective tissue. It can also spread to other parts of the body, such as lymph nodes, bones, lungs, etc. This is called metastasis. The two main types of invasive breast cancer are: 
&nbsp;

<ul>
	<li>Invasive Ductal Carcinoma - This is the most common type of breast cancer, accounting for 80% of all cases. It develops in the milk ducts.</li>
	<li>Invasive Lobular Carcinoma - This type of invasive breast cancer develops in the lobules and accounts for 10% of all invasive breast cancer cases. 
	&nbsp;</li>
</ul>

Some types of invasive breast cancer develop in different ways and have special characteristics that influence their treatment and prognosis. They are less common but can be more aggressive. These include:

<ul>
	<li>Triple-Negative Breast Cancer - Approximately 12% of all invasive cancers are of this type. This aggressive type lacks estrogen and progesterone receptors, as well as HER2 proteins. Due to the nature of the cancer cells, treatment options are quite limited. Chemotherapy is usually administered, followed by surgery. 
	&nbsp;</li>
	<li>Inflammatory Breast Cancer - This rare breast cancer accounts for 1% to 5% of all cases. Cancer cells obstruct the skin&rsquo;s lymph vessels, causing redness, swelling, pitting, and an inverted nipple. Treatment typically involves chemotherapy, followed by surgery. Radiation and other treatments are administered after surgery. Due to the cancer&rsquo;s aggressive nature, doctors do not advise breast-conserving surgery or sentinel lymph node biopsy<a href="#accordion">[12]</a>.&nbsp; 
	&nbsp;</li>
</ul>

Invasive breast cancer can also be divided into the following less common subtypes. They have a better prognosis than the common types of invasive ductal carcinomas.

<ul>
	<li>Adenoid cystic carcinoma</li>
	<li>Medullary carcinoma</li>
	<li>Papillary carcinoma</li>
	<li>Low-grade adenosquamous carcinoma</li>
	<li>Mucinous carcinoma</li>
	<li>Tubular carcinoma 
	&nbsp;</li>
</ul>

The following subtypes have a worse prognosis than invasive ductal carcinoma.

<ul>
	<li>Mixed carcinoma</li>
	<li>Metaplastic carcinoma</li>
	<li>Micropapillary carcinoma 
	&nbsp;</li>
</ul>

<h5>Others</h5>

The following are some less common types of breast cancer.

<ul>
	<li><a href="https://merisehat.pk/disease/pagets-disease-of-the-breast">Paget Disease Of The Breast</a> - Cancer begins in the ducts and spreads to the nipples and the areola. It is rare and only makes up 1-3% of all cases. The skin of the nipple and areola appears red, crusty, and scaly. Nipple discharge can also occur. Mastectomy or breast-conserving surgery is used to treat Paget&#39;s disease of the breast<a href="#accordion">[13]</a>. This is usually followed by radiation therapy. 
	&nbsp;</li>
	<li>Phyllodes Tumor - The rare breast tumor develops in the breast connective tissue (stroma). It accounts for less than 1% of all breast tumors. Although most are benign, 25% are cancerous. Benign tumors can be removed using excisional biopsy, while borderline or malignant tumors require breast-conserving surgery or mastectomy<a href="#accordion">[14]</a>. Radiation therapy may be administered after surgery. 
	&nbsp;</li>
	<li>Angiosarcoma - It develops in cells lining the blood or lymph vessels. Often at times, it results as a complication of previous radiation therapy to the breast. Purple-colored nodules may appear, along with a lump in the breast. Since angiosarcomas grow and spread swiftly, mastectomy is typically performed<a href="#accordion">[15]</a>. 
	&nbsp;</li>
</ul>

Signs and Symptoms

Some common signs and symptoms of breast cancer include:

<ul>
	<li>Lump in the breast or underarm</li>
	<li>Change in breast size or shape</li>
	<li>Redness of the skin on the breast or nipple</li>
	<li>Dimpling of the breast skin (appears like an orange peel)</li>
	<li>Swelling of all or part of a breast</li>
	<li>Swollen lymph nodes in the arm or near the collarbone</li>
	<li>Inverted or retracted nipples</li>
	<li>Clear or blood-stained nipple discharge</li>
	<li>Breast pain 
	&nbsp;</li>
</ul>

Causes

Breast cancer results from the growth and multiplication of abnormal cells. It is unclear as to what leads to the growth of these cells. However, certain factors may play a role in increasing the risk of breast cancer. 
&nbsp;

Mammography is most commonly used to screen for breast cancer. The United States Preventive Services Task Force (USPSTF) recommended mammograms every 2 years for 50 to 74-year-olds at average risk for breast cancer<a href="#accordion">[17]</a>. Whereas, 40 to 40-year-olds should consult a healthcare professional and weigh the risks and benefits of screening tests when deciding whether or not to undergo a mammogram before age 50.&nbsp;

American Cancer Society (ACS) recommends yearly mammograms in women aged 40 to 44 years<a href="#accordion">[18]</a>.

A breast MRI can be used to screen women at high risk of breast cancer. Furthermore, a clinical breast exam or a breast self-exam is also sometimes used to screen for breast cancer. 
&nbsp;

Diagnosis

A breast biopsy is the only definitive diagnostic test for breast cancer. The doctor uses a specialized needle device to extract a tissue sample from the suspected region. These samples are then analyzed for the presence and type of cancer cells. Furthermore, the cancer can then be graded. Staging and grading of the cancer enables physicians to assess its dimensions, extent of spread, and identify optimal courses of treatment. 
&nbsp;

The TNM staging system is used to stage breast cancer<a href="#accordion">[19]</a>. 
&nbsp;

Stage 0 - Also called non-invasive or in situ cancer, the disease is only present in the breast ducts and has not invaded the surrounding breast tissue. 
&nbsp;

Stage IA - This stage is characterized by an invasive tumor that has not spread to the lymph nodes. 
&nbsp;

Stage IB - The tumor is 0.2 to 2mm in size and has spread to the lymph nodes. There might be no evidence of a tumor in the breast or its smaller than 20mm. 
&nbsp;

Stage IIA - This stage requires either one of the following conditions:

<ul>
	<li>No evidence of a tumor in the breast, but 1-3 axillary lymph nodes have the cancer. No other parts of the body have cancer cells.</li>
	<li>The tumor spreads to 1-3 axillary lymph nodes and is 20mm or smaller.</li>
	<li>The tumor is 20-50 mm in size but has not spread to the axillary lymph nodes. 
	&nbsp;</li>
</ul>

Stage IIB - This stage requires either one of the following conditions:

<ul>
	<li>The tumor is 20-50 mm in size and has spread to 1-3 axillary lymph nodes.</li>
	<li>The tumor is bigger than 50mm but has not spread to any axillary lymph nodes. 
	&nbsp;</li>
</ul>

Stage IIIA - Any size tumor that has spread to 4-9 axillary lymph nodes or internal mammary lymph nodes. However, it has not spread to any other distant body parts. 
&nbsp;

Stage IIIB - The chest wall is involved, resulting in swelling or ulceration of the breast skin; or the tumor is diagnosed as inflammatory breast cancer. No other body parts are involved. However, cancer may have spread to 9 internal mammary or axillary lymph nodes. 
&nbsp;

Stage IIIC - Any size tumor that spreads to 10 or more lymph nodes, axillary, internal mammary, or under the collar bone. No distant metastasis is seen. 
&nbsp;

Stage IV - This is known as metastatic breast cancer and involves the spread of cancer to other organs (e.g., lungs, bones, liver, brain), distant lymph nodes, or chest wall. 
&nbsp;

<h5>Grading Of Breast Cancer</h5>

The grading helps assess how fast the cancer can grow and spread. Invasive breast cancer is usually graded as well-differentiated, moderately differentiated, and poorly differentiated[20].

Grade 1 Or Well-Differentiated - These cells resemble normal breast cells more and are slower-growing.

Grade 2 Or Moderately Differentiated - These cells are relatively fast-growing and start to lose their resemblance to normal breast cells.

Grade 3 Or Poorly Differentiated - Cancer cells do not resemble normal cells and grow and spread very quickly. 
&nbsp;

Treatment

The treatment likely depends on the person&rsquo;s overall health, the stage of the breast cancer, the type of breast cancer, and several other factors. 
&nbsp;

The following types of surgical procedures are used to treat breast cancer.

<ul>
	<li>Lumpectomy</li>
	<li>Mastectomy</li>
	<li>Sentinel node biopsy</li>
	<li>Axillary lymph node dissection</li>
	<li>Modified radical mastectomy</li>
	<li>Radical mastectomy 
	&nbsp;</li>
</ul>

Other treatment options include:

<ul>
	<li>Chemotherapy</li>
	<li>Radiation therapy</li>
	<li>Hormone therapy</li>
	<li>Immunotherapy</li>
	<li>Targeted drug therapy 
	&nbsp;</li>
</ul>

Some common complications of breast cancer are:

<ul>
	<li>Sleep disturbances</li>
	<li><a href="https://merisehat.pk/disease/anxiety">Anxiety </a>or <a href="https://merisehat.pk/disease/depression">depression</a></li>
	<li>Loss of sexual interest</li>
	<li>Secondary cancers</li>
	<li>Heart damage 
	&nbsp;</li>
</ul>

Complications can also arise from surgery and chemotherapy. These include lymphedema, hematoma, reactions to anesthesia, hair loss, nausea, dry mouth, and infertility. 
&nbsp;

The following factors can increase the risk of breast cancer:

<ul>
	<li>Age - The risk increases with age, especially after 50 years of age.</li>
	<li>Gender - Women have a higher incidence of breast cancer than men.</li>
	<li>Family history -&nbsp; Having a family member with breast cancer increases the risk of breast cancer.</li>
	<li>Genetics - Certain gene mutations, such as BRCA1 and BRCA2 greatly increase the risk of breast cancer.</li>
	<li><a href="https://merisehat.pk/disease/obesity">Obesity</a></li>
	<li>Smoking</li>
	<li>Alcohol use</li>
	<li>Radiation exposure</li>
	<li>Hormone replacement therapy 
	&nbsp;</li>
</ul>

The following measures can help reduce the risk of breast cancer:

<ul>
	<li>Regular breast self-exams or mammograms</li>
	<li>Quitting smoking and alcohol</li>
	<li>Daily exercise</li>
	<li>Avoiding postmenopausal hormone therapy</li>
	<li>Maintaining a healthy weight</li>
	<li>Eating a healthy diet 
	&nbsp;</li>
</ul>

A recent study compared the sensitivity of artificial intelligence (AI) to digital mammography for the detection of different types of breast cancer<a href="#accordion">[21]</a>. The AI model had a higher sensitivity and lower false negative rates than mammography in detecting ductal carcinoma in situ and invasive lobular carcinoma. Moreover, AI was able to detect breast cancer with challenging morphology, such as suspicious calcification and asymmetry. 
&nbsp;

Key Points

<ul>
	<li>Breast cancer is defined as the growth of cancer cells within the breast tissues, ducts, or lobules.</li>
	<li>Breast cancer is the most common cancer worldwide and a leading cause of death in women.</li>
	<li>Depending on where the cancer originates, how much it has grown or spread, and how it behaves, breast cancer can be classified into various types.</li>
	<li>In-situ or non-invasive breast cancer refers to cancer that has not spread beyond its point of origin. They are also called precancers. It includes ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS).</li>
	<li>Ductal carcinoma in situ (DCIS) accounts for 16% of all breast cancer cases. Cancer originates in the milk ducts but does not spread outside</li>
	<li>Invasive breast cancer refers to breast cancer that grows outside of the normal ducts and lobules into the breast connective tissue. It can also spread to other parts of the body, such as lymph nodes, bones, lungs, etc.</li>
	<li>Invasive ductal carcinoma is the most common type of breast cancer, accounting for 80% of all cases.</li>
	<li>Some types of invasive breast cancer develop in different ways and have special characteristics that influence their treatment and prognosis. They are less common but can be more aggressive. These include inflammatory breast cancer, Paget disease of the breast, and triple-negative breast cancer.</li>
	<li>Breast cancer results from the growth and multiplication of abnormal cells. It is unclear as to what leads to the growth of these cells.</li>
	<li>Mammography is most commonly used to screen for breast cancer.</li>
	<li>A breast biopsy is the only definitive diagnostic test for breast cancer.</li>
	<li>The treatment likely depends on the person&rsquo;s overall health, the stage of the breast cancer, the type of breast cancer, and several other factors. 
	&nbsp;</li>
</ul>

[1] NCI Dictionary of Cancer terms. National Cancer Institute.

[2] Arnold M, Morgan E, Rumgay H, et al. Current and future burden of breast cancer: Global Statistics for 2020 and 2040. The Breast. 2022;66:15-23. doi:10.1016/j.breast.2022.08.010

[3] Pavani Chalasani M. Breast cancer. Practice Essentials, Background, Anatomy.

[4] Smolarz B, Nowak AZ, Romanowicz H. Breast Cancer-Epidemiology, Classification, Pathogenesis and Treatment (Review of Literature). Cancers (Basel). 2022;14(10):2569. Published 2022 May 23. doi:10.3390/cancers14102569

[5] Saeed, S., Asim, M. & Sohail, M.M. Fears and barriers: problems in breast cancer diagnosis and treatment in Pakistan. BMC Women's Health 21, 151 (2021).

[6] Khan NH, Duan SF, Wu DD, Ji XY. Better Reporting and Awareness Campaigns Needed for Breast Cancer in Pakistani Women. Cancer Manag Res. 2021;13:2125-2129. Published 2021 Mar 2. doi:10.2147/CMAR.S270671

[7] Konduri S, Singh M, Bobustuc G, Rovin R, Kassam A. Epidemiology of male breast cancer. Breast. 2020;54:8-14. doi:10.1016/j.breast.2020.08.010

[8] Zeeshan S, Siddiqiui T, Shaukat F, et al. (February 27, 2022) Male Breast Cancer: The Three Decades' Experience of a Tertiary Care Hospital in a Lower-Middle Income Country. Cureus 14(2): e22670. DOI 10.7759/cureus.22670

[9] Types of Breast Cancer. Breastcancer.org.

[10] American Cancer Society. Treatment of ductal carcinoma in situ (DCIS). Information and Resources about for Cancer: Breast, Colon, Lung, Prostate, Skin.

[11] American Cancer Society. Types of breast cancer. About Breast Cancer.

[12] American Cancer Society. Inflammatory breast cancer.

[13] American Cancer Society. Paget disease of the breast.

[14] American Cancer Society. Phyllodes Tumors of the Breast

[15] American Cancer Society. Angiosarcoma of the Breast

[16] American Cancer Society. Invasive Breast Cancer (IDC/ILC)

[17] What is breast cancer screening? Centers for Disease Control and Prevention.

[18] Breast cancer - screening. Cancer.Net.

[19] Breast cancer - stages. Cancer.Net.

[20] American Cancer Society. What is a breast cancer’s grade?: Grading breast cancer. What Is a Breast Cancer’s Grade? | Grading Breast Cancer.

[21] Raafat, M., Mansour, S., Kamal, R. et al. Does artificial intelligence aid in the detection of different types of breast cancer?. Egypt J Radiol Nucl Med 53, 182 (2022).