Types of Breast Cancer
There are several different types of breast cancer. Breast cancers can be categorized based on a number of characteristics including their cell of origin, a unique identify finding when viewed under the microscope or some other set of characteristics. At Alaska Breast Care and Surgery, we have experience in treating all the different subtypes of breast cancer.
Invasive ductal carcinoma (IDC), sometimes called infiltrating ductal carcinoma, this is the most common type of breast cancer. About 80% of all breast cancers are invasive ductal carcinomas. It arises from the cells that line the milk ducts. Milk ducts take milk made in breast lobules out to the nipple. According to the American Cancer Society, more than 180,000 women in the United States find out they have invasive breast cancer each year. Most of these newly diagnosed breast cancers will be invasive ductal carcinoma.
Tubular carcinoma of the breast is a subtype of invasive ductal carcinoma (cancer that begins inside the milk). The name tubular carcinoma comes from the appearance of the tumor under the microscope. The pathologist will see tube-shaped structures called "tubules”. These tumors tend to be small (about 1 cm or less) and low-grade, meaning that their cells look somewhat similar to normal, healthy cells. These lesions also tend to grow slowly. It also in uncommon for it to spread to other areas away from the breast. All of these factors give tubular carcinomas a favorable prognosis relative to other breast cancers. It does seem that tubular carcinomas, although still rare, are becoming more common. We think the most likely explanation for this is the wide spread use of screening mammogram as these lesions are commonly picked up on a screening mammogram.
Studies also suggest that the average age of diagnosis for tubular carcinoma is the early 50s, although women can be diagnosed with it at any age. This type of cancer is rare in men.
Medullary carcinoma of the breast is a rare subtype of invasive ductal carcinoma (cancer that begins in the milk duct). The name comes from the texture and appearance of the tumor. The tumor is soft and fleshy. Early pathologist thought it resembled the medulla of the brain and hence called in medullary carcinoma.
Medullary carcinoma tends to be seen in women their late 40s and early 50s but it can occur at any age. Medullary carcinoma is more common in women who have a BRCA1 mutation. Studies have shown that medullary carcinoma is also more common in Japan than in the United States. About 3 to 5% of breast cancers are medullary cancers.
Medullary carcinoma cells are usually high-grade in their appearance and low-grade in their behavior. That means that they look like aggressive, highly abnormal cancer cells, but they don’t act like them. Reassuringly, medullary cancers tend to grow more slowly and it tends not to spread to the lymph nodes. Cancers that have not spread to the lymph nodes have a better prognosis than cancers that have spread. This gives medullary carcinoma a relatively favorable prognosis. Some postulate that the body’s immune response may help to explain why medullary carcinomas are less likely to have lymph node metastasis then similar invasive ductal carcinomas. This is just a theory, but an intriguing one.
Mucinous carcinoma of the breast — sometimes called colloid carcinoma — is a rare form of invasive ductal carcinoma (cancer that begins in the milk duct). In mucinous breast cancer, the tumor is made up of malignant cells that “float” in pools of mucin. Mucous membranes secrete mucins to help form a protective barrier. It is a component of mucus. When examined under a microscope, one can see pools of mucin within the breast tumor.
Although mucinous breast cancer can be diagnosed at any age, it tends to affect women after they’ve gone through menopause. Some studies have found that the average age at diagnosis is in the 60s or early 70s. This type of cancer accounts for about 2% of all breast cancers though another 5% of invasive breast cancers will have a mucinous component.
Even though mucinous carcinoma is an invasive breast cancer, it tends to be a less aggressive type that responds well to treatment. Mucinous carcinoma is less likely to spread to the lymph nodes than other types of breast cancer and have a better prognosis.
Invasive papillary carcinoma of the breast is rare form of invasive ductal carcinoma breast cancer. The name comes from its appearance under the microscope. This tumor forms small, finger-like projections. These “papules” give papillary carcinoma its name.
Invasive papillary carcinoma should not be confused with intraductal papillomas. Intraductal papillomas are a benign condition. However, sometimes the pathologist needs to look at the entire papilloma to make sure that it is not a papillary carcinoma. In these cases, where the concern is high enough to warrant excision, the papilloma will be recommended for excision rather than observation.
Papillary carcinomas of the breast tend to be small, less likely to involve the lymph nodes and more responsive to treatment. They may have a better prognosis than more common types of invasive ductal carcinoma. These lesions tend to be estrogen and progesterone receptor positive.
Invasive papillary tumors are most commonly seen in postmenopausal women. In most cases of invasive papillary carcinoma, ductal carcinoma in situ (DCIS) is also present. (DCIS is a type of cancer in which the carcinoma cells are confined to the breast duct.) It accounts for less than 1% of all breast cancers.
Invasive lobular carcinoma (ILC), sometimes called infiltrating lobular carcinoma, is the second most common type of breast cancer after invasive ductal carcinoma (cancer that begins in the milk ducts). According to the American Cancer Society, more than 180,000 women in the United States find out they have invasive breast cancer each year. About 10% of all invasive breast cancers are invasive lobular carcinomas. (About 80% are invasive ductal carcinomas.)
Invasive lobular carcinomas arise from the cells that line the sacs in the breast that make the milk. These sacs that make milk are called lobules.
Although invasive lobular carcinoma can affect women at any age, this form of cancer becomes more common as women grow older.
Post-menopausal hormone replacement therapy can significantly increase the risk of invasive lobular carcinoma. This is based on both a series of individual epidemiologic studies and a meta-analysis of those studies that suggest that the relative risk of invasive lobular compared to invasive ductal cancer is approximately doubled when post-menopausal women are taking combined hormone replacement therapy (HRT).
Paget's disease is a rare form of breast cancer where tumor cells, typically of ductal origin, cause skin changes to the nipple and adjacent areola (the pigmented disk around the nipple). The nipple and areola often become scaly, red, itchy, and irritated. The vast majority of patients with Paget’s disease of the nipple have DCIS or invasive breast cancer elsewhere in their breast. AN important part of the assessment of a patient with Paget’s disease of the nipple is a careful look for disease elsewhere in the breast.
Most patients with scaly, itchy red patches around their nipples have eczema. Eczema is common whereas Paget’s is an uncommon condition. However, it is important to treat all cases of eczema and dry skin that involve the nipple and areola. If the dry scaly patches do not clear up, then a work-up that includes a skin biopsy may be indicated. We find that dry, itchy nipples can become quite an issues up here in Alaska in the winter. It is likely attributed to the harsh dry winter air and a tendency for women to take even hotter and longer showers during the winter months.
Paget's disease of the nipple is more common in women, but like other forms of breast cancer, it can also affect men. The disease usually develops after age 50 with the average age of diagnosis being in the sixties.
Metaplastic breast cancer is a rare form of breast cancer, accounting for fewer than 1% of all breast cancers. Like invasive ductal cancer, metaplastic breast cancer begins in the milk duct of the breast before spreading to the tissue around the duct. However, when the cells of an invasive ductal tumor are examined under a microscope, they appear abnormal, but still have features that identify them as ductal cells. Metaplastic tumors may contain some of these ductal cells, too, but they also contain cells that look like the supporting tissues around the milk ducts. Scientist believe that the ductal cells have undergone a change in form (metaplasia) to become completely different cells (cancerous connective tissue and soft tissue cells). It is not known exactly how or why this occurs.
Metaplastic breast cancers can also behave more aggressively than other kinds of breast cancers. They are often high grade which means they look very different from normal cells. They are often, though not always, “triple-negative” which means that they test negative for estrogen and progesterone receptors, as well as for the HER2/neu protein. Metaplastic tumors are more likely than other kinds of breast cancer to have metastasis (when the cancer has spread beyond the breast).
Apocrine breast cancer is a rare type of invasive ductal breast cancer. Like other types of invasive ductal cancer, apocrine breast cancer begins in the milk duct of the breast before spreading to the tissues around the duct. When the cells of an apocrine tumor are examined under the microscope, they have features that are similar to cells that make up the sweat glands that are found in the arm pit and the groin. It is thought that the normal ductal breast cells have undergone a change to form a different cell type. They have changed from ductal cells to apocrine cells. This change is called metaplasia. It is not known exactly how or why this occurs.
Apocrine tumors are often “triple negative”, meaning that the cells do not express the estrogen receptor, progesterone receptor, or HER2/neu receptor. Apocrine tumor cells are almost always positive for an additional receptor called the androgen receptor. Apocrine tumors, even when triple negative, are less likely to involve the lymph nodes, are more responsive to treatment, and may have a better prognosis than more common types of invasive ductal cancer.
Adenoid cystic breast cancer is an extremely rare type of invasive ductal breast cancer which accounts for less than 1% of all breast cancers. When the cells of an adenoid cystic tumor are examined under the microscope, they look like cancer cells more commonly found in the salivary glands. Age range in the reported literature ranges from 19 to 94 years old so it spans all age groups.
Adenoid cystic tumors are often “triple negative”, meaning that the cells do not express the estrogen receptor, progesterone receptor, or HER2 receptor. Even when triple negative, adenoid cystic breast cancers are less likely to involve the lymph nodes, are more responsive to treatment, and may have a better prognosis than more common types of invasive ductal cancer. When they do recur, local recurrence is more common than distant or metastatic recurrence.
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