The Different Types of Breast Cancer, Explained

August 27, 2023

Breast cancer is a type of cancer that forms in the breast tissues and is regarded as the most common type of cancer in women. Although it is one of the most studied, the causes have not been fully known, but the risk factors are identified. Some of the risk factors include obesity, lack of exercises, family history, and age. It occurs in both women and men but is far more common in women.

In the United States alone, about twelve percent of women develop breast cancer in their lifetime. The first warning sign is usually a lump or thickening in the breast that differs from the surrounding tissues. Other symptoms include a change in breast shape, inverted nipple, and dimpling. However, the symptoms vary from person to person.

In Situ Breast Cancers

Ductal carcinoma in situ (DCIS) is the main type of in situ breast cancers. The DCIS is non-invasive breast cancer that occurs in the milk ducts, and the cells have not spread to other tissues of the breast. DCIS is treatable when identified early, though it increases the risk of developing invasive cancer. There is a possibility DCIS can reoccur after treatment, but the chances are below thirty percent. Those who have had a lumpectomy without radiation therapy have a high likelihood of having a reoccurrence. Studies have shown the therapy significantly reduces risks of reoccurrence. The American Cancer Society indicates there are over sixty thousand cases of DCIS diagnosed annually.

Although lobular carcinoma in situ (LCIS) is not considered cancer, it is a condition where abnormal cells develop in the milk glands and increase the risk of invasive breast cancer. In most cases, it is discovered by biopsy because it does not show any symptoms or on the mammogram. Paget disease is not common and mostly affects the nipple. It first affects the ducts of the nipple before spreading on the surface around the nipple. Some of the symptoms include itchy and inflamed skin, discharge, burning sensation, and inversion of the nipple. According to the National Cancer Institute, Paget disease is only responsible for one to four percent of breast cancer cases.

Invasive Breast Cancers

Invasive breast cancers mean the cancerous cells have migrated to other parts of the breast or the body. Two main categories of invasive breast cancers are invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC). They are the most common types of breast cancers and account for about eighty percent of all cases. The American Cancer Society indicates over one hundred and eight women are diagnosed with invasive breast cancer annually.

IDC is the most common invasive breast cancer and mostly affects older women. However, it can affect women of any age and can affect men as well. The American Cancer Society reports the majority of the women who have been diagnosed with the cancer are over fifty-five years old. ILC accounts for about ten percent of invasive breast cancer. It occurs in the lobule and spreads to other breast and body tissues. Unlike other types of cancer, it does not cause a lump and is therefore hard to detect. However, it can be identified through a mammogram, ultrasound, MRI, or biopsy. ILC occurs later than IDC, especially after sixty years.

Rare Breast Cancers

The most common types of breast cancers develop from the ducts or lobules. Conversely, rare types of breast cancer form in other tissues and cells of the breast, including the sebaceous glands, endothelial cells, and muscles. The therapeutic approach to the treatment of primary breast cancer is extensively studied and well defined. However, there is no consensus regarding treatment of rare breast cancer due to the rarity in research, and most of them have been treated with standard therapy. Some of the most common rare breast cancers include secretory carcinoma, neuroendocrine carcinoma, invasive cribriform carcinoma, mucinous carcinoma, solid papillary carcinoma, and apocrine carcinoma.

Breast Cancer Subtypes

Although most people think breast cancer is one type of disease, studies have shown there are multiple subtypes. The subtypes are classified according to the tumor, nodes, and metastasis. Their growth rates and risk factors vary. Below are some of the five main breast cancer subtypes. Luminal A is a subtype of breast cancer that is hormone-receptor positive and HER2 negative. It also has reduced levels of protein Ki-67, which determines the growth rate of the cancer cells. They have slow growth and good prognosis. Similar to Luminal A, Luminal B is hormone-receptor positive. However, it is also HER2 positive or HER2 negative and elevated amount of Ki-67. Additionally, it grows faster and has a poor prognosis.

Triple-negative (basal-like) is both hormone-receptor and HER2 negative. It is mostly associated with women with BRCA1gene mutations. Research has shown it is prevalent among young and African-American women. The HER2-enriched subtype is hormone-receptor negative and HER2 positive. They grow faster than other subtypes and also have a poor prognosis. Nevertheless, it is treatable with effective therapies on the HER2 proteins. Normal-like breast cancer is hormone-receptor positive, HER2 negative, and has reduced levels of Ki-67 protein. Compared to other subtypes, it has an excellent prognosis, but still poorer than Luminal A.

Metastatic Breast Cancer

Metastatic breast cancer is an indication cancer has migrated from the breasts to other parts of the body. Some of the common sites the disease manifests include the lungs, liver, bones, and brain. It occurs several months or years after primary cancer, and sometimes, it is a re-occurrence of the breast cancer after diagnosis and treatment. Almost three in ten women diagnosed with breast cancer will develop metastatic disease.

Cancer cells from the breast travel to other parts of the body either through the bloodstream or the lymphatic system. Although it can be managed and treated, thus extending the patient's life, it cannot be cured. Some of the treatment options include surgery, radiation, and hormonal therapy The symptoms and treatment options mainly depend on the site of the tumors. Metastatic breast cancer is the most significant cause of death for breast cancer patients, accounting for about ninety percent of all cases.

Inflammatory Breast Cancer

Inflammatory breast cancer a form of breast malignancy where cancerous cells cause an obstruction in the lymph vessels in the skin of an affected individual's breast. This form of breast cancer accounts for between one and five percent of all breast cancers diagnosed in the United States. The majority of inflammatory breast cancers are those that have developed from the cells making up the lining of an individual's milk ducts that have spread into surrounding lymph tissues and are referred to as invasive ductal carcinomas.

Most individuals diagnosed with inflammatory breast cancer are already in stage III or IV at the time of diagnosis because it spreads rapidly. Most inflammatory breast cancers cannot be treated with the use of hormone therapies or are considered hormone receptor-negative. Compared to other forms of breast cancer, inflammatory breast cancer tends to occur in women of younger ages. The symptoms that distinguish inflammatory breast cancer from other types are redness and swelling of over thirty-three percent of the breast.

Subtypes Of Invasive Ductal Carcinoma

Invasive ductal carcinoma is the most common form of breast cancer where cancerous cells have developed from the cells that line the milk ducts and have metastasized to surrounding structures. The milk ducts in the breast are the small tubes that carry milk from the lobules producing the milk to the nipple. Tubular carcinoma is a subtype of invasive ductal carcinoma where the tumor measures one centimeter or less and possesses tubule characteristics. Medullary carcinoma is a subtype of invasive ductal carcinoma where the tumor resembles a soft structure of the brain referred to as the medulla.

Mucinous carcinoma is a subtype of invasive ductal carcinoma where the abnormal cells are suspended in pools of mucin or the main component of mucus. Papillary carcinoma is a subtype of invasive ductal carcinoma where the tumor has fingerlike projections and a well-defined border. Cribriform carcinoma is a subtype of invasive ductal carcinoma where the malignant cells infiltrate the connective tissues in the breast in nest-like arrangements between the lobules and ducts.

Male Breast Cancer

Male breast cancer is a rare malignancy that occurs in the breast tissue of a male. Male breast cancer accounts for less than one percent of all diagnosed breast cancers. Men who take hormonal medications, are overweight, drink excessive amounts of alcohol, have liver disease, and have been exposed to environmental estrogens are at a higher risk of developing male breast cancer. Men who are affected by Klinefelter syndrome, have abnormal BRCA1 or BRCA2 genes, or have been exposed to radiation are also more likely to develop male breast cancer.

The most common symptoms of male breast cancer include a lump in the breast, inverted nipple, sores on areola or nipple, enlarged lymph nodes in the armpit, nipple pain, and nipple discharge. Male breast cancer is diagnosed in the same ways other breast cancers are diagnosed: with the use of physical examination, mammogram, ultrasound, nipple discharge examination, and tissue biopsy. Male breast cancer is treated with surgery, radiation therapy, hormonal therapy, targeted therapy, and chemotherapy.

Breast Cancer Hormone Status

Cells from breast cancer will be extracted during surgery to remove the tumor or during a biopsy so they can be sent to a laboratory and examined by a pathologist under a microscope and tested to see if they contain progesterone or estrogen receptors. These receptors on cancerous breast cancer cells provide a way for progesterone and estrogen to fuel the growth of the tumor. Malignant breast tumors containing estrogen receptors are referred to as ER-positive breast cancers. Malignant breast tumors with progesterone receptors are referred to as PR-positive breast cancers.

The term hormone receptor-positive breast cancer refers to any malignancy with one or both receptors for progesterone and estrogen. The term hormone receptor-negative breast cancer refers to a malignancy with no receptors for estrogen or progesterone. Information regarding breast cancer hormone status is extremely helpful when determining how to treat a patient's breast cancer. Certain hormone therapy drugs can be utilized to reduce the estrogen levels or block the estrogen from acting on breast cancer cells in most hormone receptor-positive tumors.

Phyllodes Tumor

Phyllodes tumor describes rare tumors that develop in breast tissue that grow in a leaf-like arrangement and account for less than one percent of all diagnosed breast tumors. Phyllodes tumors differ from other types of breast tumors because they do not develop from the cells of an individual's milk ducts or in the cells making up the milk-producing glands or lobules of the breast. Phyllodes tumors develop in the cells that make up the connective tissues inside the breast (stroma), which include the ligaments and fatty tissues that encapsulate and surround the lobules, blood vessels, milk ducts, and lymph vessels in the breast.

The most common indication of a phyllodes tumor is a palpable lump or mass that can be felt during a breast examination. Phyllodes tumors tend to grow rapidly, reaching a size of between two and three centimeters in just a matter of weeks or months. Phyllodes tumors can be more challenging to diagnose than other types of breast cancer because they are so rare. A physical exam, mammogram, ultrasound, MRI scan, and tissue biopsy are used to make a phyllodes tumor diagnosis.

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