In October We Wear Pink: An Introduction to Breast Cancer
Author: Ashlyn Jimenez
Editor: Becky Gold
As many know, October is Breast Cancer Awareness month! This month we will be presenting multiple topics in the breast cancer world. To kick it off, we want to discuss the different types of breast cancer and their defining features.
Malignant breast tumors occur more commonly in post-menopausal women; however, a family history of breast cancer makes breast changes in younger women more concerning. Additional risk factors for breast cancer include BRCA (and many other) gene mutations, older age of first live birth, African American ethnicity, and increased estrogen exposure. Increased estrogen exposure can come from many sources such as increased total number of menstrual cycles throughout life, hormone therapy, or obesity (fat cells convert androstenedione to estrone, a form of estrogen).
Breast malignancies are called carcinomas. A carcinoma is any cancer that develops in the cells that make up the skin or the tissue lining organs, such as the breast tissue. Before we trudge forward, let’s take a quick moment to review breast cancer anatomy.
This is far and away the most common breast cancer, accounting for almost 76% of all invasive breast cancers. This can present as ductal carcinoma in situ or as invasive/infiltrating ductal carcinoma. The name itself already describes many of its features. Ductal carcinoma in situ, or DCIS, means that this type of cancer has not yet invaded through its normal tissue--”in situ” means “in the original place.” Infiltrating, or invasive, ductal carcinoma means that the cancer has invaded, or infiltrated, through its normal tissue line.
The cancer starts in the lactiferous (milk) ducts--the ducts that carry milk from the lobules to the nipples. The mass will feel firm, sometimes described as “rock hard”, with well defined edges that invade the surrounding tissue in a haphazard fashion, creating a stellate shape. Microscopically these tumors characterized by cords and nests of tumor cells with gland formation.
Lobular carcinoma makes up about 10% of all invasive breast cancer. This too can present as either lobular carcinoma in situ (not yet invasive) or as invasive lobular carcinoma. Lobular carcinoma is a cancer that develops from the milk-producing lobules of the breast. This type of breast cancer will often occur on both breasts with multiple nodules in the same location. Under the microscope, one can observe rows of cells that appear in a linear pattern.
Mixed Ductal-Lobular Carcinoma
Some breast tumors can present with mixed features of both invasive ductal and invasive lobular carcinomas. These tumors make up about 7% of all invasive breast cancers.
Mucinous Carcinoma (Colloid Carcinoma)
Mucinous (sometimes called colloid) carcinoma is a rare form of invasive ductal carcinoma and makes up about 2.5% of invasive breast cancers. Mucus is a slippery substance that is secreted by a variety of cells that line many inner surfaces of our bodies including: lungs, liver, digestive tract, and ducts in the breasts. In this carcinoma, mucus secreting cells make up the tumor. The mucous will surround the breast cancer cells. Under a microscope, the cancer cells will appear to be floating in pools of mucin--an ingredient in the normal production of mucus. In general, mucinous carcinoma is less likely to spread to lymph nodes than other forms of breast cancer.
Unlike many of the other carcinomas we have mentioned thus far, tubular carcinoma of the breast, while very rare, more commonly affects younger women (before age 50) and very rarely affects women after menopause. It makes up only 1.5% of breast cancers. Since this type of breast cancer is so rare, research is limited. These tumors are usually small (less than 1cm) and are made up of tube shaped cells. When these types of carcinomas are diagnosed, they tend to be slow growing and respond well to treatment.
Medullary breast cancer, which makes up about 1% of breast cancers, is also another subtype of invasive ductal carcinoma. It is named such because when pathologists were first examining these tumors, they noticed that it resembles the soft grayish tissue of the medulla of the brain, also known as the brainstem. Under microscopy it looks fleshy and cellular with lymphocytic infiltrates (seen in the picture below). Medullary carcinoma is slightly more common in people who carry the BRCA-1 mutation. In contrast to tubular carcinomas, medullary carcinomas are usually rapidly dividing and are often “triple negative”, meaning they test negative for estrogen and progesterone receptors as well as negative for HER2 protein. Triple-negative breast cancers are notoriously difficult to treat. Despite being triple negative and rapidly dividing, medullary carcinomas rarely involve the lymph nodes and rarely metastasize.
Papillary carcinomas are one of the most rare forms of invasive breast carcinomas, and they make up less than 1% of breast cancers. Their name comes from their finger like projections (papules) seen under microscopy.
Dermatologic conditions in breast cancer
Paget Disease of the Breast
This skin condition results from underlying ductal carcinoma in-situ (DCIS) or invasive breast cancer and only occurs in about 1-3% of these cases. It is believed that the Paget cells are intraepithelial cells that arise from underlying carcinomas by migrating through the lactation ducts into the superficial skin of the nipple. The hallmark of Paget disease of the breast is a scaley, raw lesion that begins on the nipple and spreads outward. It is sometimes described as a “weeping eczema.” It is not uncommon for pain and burning to occur before any skin changes are noted.
Inflammatory Breast Cancer
Inflammatory breast cancer, a rare and aggressive form of cancer, can occur when a breast carcinoma invades the dermal lymphatic drainage, or lymph drainage of the skin. This invasion leads to its characteristic Peau d’orange (orange peel) skin that is a result of edema causing tightening of the breasts’ suspensory ligaments, called Cooper’s Ligaments. Unfortunately, inflammatory breast cancer has a poor prognosis with only a 50% survival rate at 5 years. Typically the patient will present with breast pain or a rapidly growing lump. Almost all women with inflammatory breast cancer already have involvement of the lymph nodes at initial diagnosis.
These are just an overview of the many different types of invasive breast cancers. Often times “lumps and bumps” felt in the breast are benign (non-cancerous) and are considered normal breast variations. These benign breast bumps can be many different things, from fibrocystic breast changes, inflammatory processes, or benign tumors.
With so many different types of breast cancer, it’s no wonder that so many new discoveries are being made every day in the breast cancer world!
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