No matter where in the body cancer occurs, it happens due to mutations that take place in the genes that control cell growth. These mutations allow the cells to divide and multiply in an unregulated manner, causing cancer. Breast cancer usually develops in either the ducts or the lobules of the breast. Cancer can also develop in the fibrous connective tissue or the fatty tissue inside the breast. The uncontrolled spread of the cancer cells often ends up affecting and invading other healthy breast cells as well, sometimes traveling to the lymph nodes located under the arms. ^(1,2,3)

There are many types of breast cancer, some of which are very challenging to treat, while some are relatively less difficult to cure. Let us look at the different types of breast cancer and which one is the most curable.

Types of Breast Cancer

There are many types of breast cancer. These types are typically divided into two major categories depending on whether they are invasive or non-invasive. Non-invasive breast cancer is sometimes also referred to as breast cancer in situ. Invasive cancer tends to spread from the breast glands or ducts to other areas of the breast, while non-invasive cancer does not spread from the original infected tissue.

These two broad categories of breast cancer are used to refer to the most common types of breast cancer. One of the most common ways that doctors use to classify breast cancer depends on the area in the body where the disease started or spread. Some of these include:

Adenocarcinoma and Carcinoma: Carcinomas are a type of breast cancer that begins in the tissues that line the breasts and other organs in the body. Carcinomas are the most common type of breast cancer. Some breast cancers can be a type of carcinoma known as adenocarcinoma, which starts in the cells that line the milk ducts. When these carcinomas begin in the milk ducts, they are known as ductal carcinoma. When they start in the glands or lobes that produce milk, they are known as lobular carcinoma. ^(4,5)
Ductal Carcinoma: As mentioned above, ductal carcinoma is a type of breast cancer that begins in the cells lining the milk ducts. ^(6,7)
Ductal Carcinoma In Situ (DCIS) is one of the earliest types of ductal carcinoma. In situ means that the cancer is only present in the milk ducts, and the disease is not likely to spread to other parts of the body. It is estimated that one in five people who have been newly diagnosed with breast cancer have this type of breast cancer. Ductal carcinoma in situ is one of the most curable forms of breast cancer. ⁽⁸⁾
Invasive Ductal Carcinoma (IDC) is another very common form of breast cancer. This type of breast cancer affects around 80 percent of all people who are diagnosed with breast cancer. The term invasive means that the cancer has spread outside of the milk duct, which is where it started. ^(9,10)

There are many subtypes of invasive ductal carcinoma as well that exist. These include:

Lobular Carcinoma: In this type of invasive ductal carcinoma, the abnormal cells start growing in the lining of the milk-producing glands or lobules in the breast. Invasive lobular carcinoma (ILC) is a very prevalent form of breast cancer, and it is known as the second most common type of breast cancer to be diagnosed in the United States. Nearly ten percent of all invasive breast cancers fall under this category. Invasive lobular carcinoma typically begins in the lobules and then spreads to the surrounding tissue. This type of breast cancer can also spread to your lymph nodes and other parts of the body. ILC is also known as infiltrating lobular carcinoma due to its potent ability to spread to other parts. ^(10,11)
Cribriform Carcinoma: This is a rare form of breast cancer. It is known for its unique pattern of holes that exist between the cancer cells. It is estimated that just around five to six percent of all invasive breast cancers are of this type. ^(12,13)
Medullary Carcinoma: This is another rare type of invasive breast cancer that affects less than five percent of all cases of breast cancer. It is termed as medullary because it appears like the grayish tissue in the brain known as the medulla. ^(14,15)
Mucinous Carcinoma: Another form of invasive breast cancer is mucinous carcinoma. Mucin can be found in mucus, which is the slimy compound that prevents your tissues and organs from drying. In this type of breast cancer, there is a lot of mucin present around the cancer cells. Around two percent of all breast cancers are truly confirmed as being mucinous carcinoma. This type of breast cancer is also known as colloid carcinoma. ^(16,17)
Papillary Carcinoma: This type of breast cancer is named papillary due to the finger-like growths known as papules that tend to protrude out from these cancer cells. This is a very rare form of cancer, and only around one percent of breast cancers are confirmed as papillary carcinomas. This type of cancer usually affects older women more. (18,19)
Tubular Carcin oma: Just around one to two percent of all invasive breast cancers are diagnosed as tubular carcinoma. The cancer gets its name from the tube-like structures present inside the cancer cells. This type of cancer tends to progress slowly and is very treatable. ^(20,21)

Some other types of breast cancer are:

Inflammatory Breast Cancer: This rare form of breast cancer accounts for only around five percent of all cases. The symptoms of inflammatory breast cancer are different from those of the other types of breast cancer as the cancer cells in this cancer block the lymphatic vessels located in the breast. These are similar to the blood vessels in the body, except they carry lymphatic fluid. This blockage of the vessels causes the skin to turn red, become swollen, and also thicken. Certain parts of the breast might even appear similar to the skin of an orange. Inflammatory breast cancer tends to spread very rapidly. ^(22,23)
Metastatic Breast Cancer: The term metastatic means that cancer has already spread beyond the breast area. Doctors call this as advanced or stage 4 breast cancer. The most common parts for this form of breast cancer to spread to are the liver, bones, lungs, or even the brain. ^(24,25)

There are some less common types of breast cancer as well that exist. These include:

Angiosarcoma: This is a rare type of breast cancer that grows on the lymph vessels or the blood vessels in the breast. ⁽²⁶⁾
Paget Disease of the Nipple: This type of breast cancer starts in the ducts of the nipple. However, as the cancer starts to grow, it begins affecting the skin and areola of the nipple as well. ⁽²⁷⁾
Phyllodes Tumor: This is a very rare type of breast cancer that grows within the connective tissue of the breast. Most of the phyllodes tumors are usually benign, but some do turn out to be cancerous. ⁽²⁸⁾

After getting diagnosed with breast cancer, your doctor will carry out certain tests on your cancer cells to determine whether they grow in response to various hormones, including progesterone or estrogen, or whether they contain specific genes. These tests are performed so that your doctor can find the best-suited treatment for you that is designed to work well against your individual type of cancer. Here are some types of breast cancer that are diagnosed based on the genes or hormones.

HER2 Positive: Nearly one out of five cases of breast cancer tests positive for the presence of human epidermal growth factor receptor 2 (HER2). This is a type of protein that helps the cancer cells grow and spread. Breast cancers that test positive for HER2 are usually more aggressive than other types. For treating this type of breast cancer, doctors use a class of drugs that includes trastuzumab and pertuzumab (brand name Perjeta). ^(29,30)
Triple Negative Breast Cancer: Approximately 15 percent of all breast cancers fall in this category. Triple-negative breast cancer does not have the receptors for HE2, progesterone, or estrogen. This is what makes it much more challenging to treat. ^(31,32)

What Type of Breast Cancer is Most Curable?

Once your breast cancer type has been identified, your doctor will discuss your outlook and treatment options with you. As mentioned above, ductal carcinoma in situ is the most easily curable form of breast cancer.

The treatment of ductal carcinoma in situ has a very high chance of success, and in most cases, the removal of the tumor can prevent the recurrence of cancer. For most people, treatment of this type of breast cancer usually includes:

Breast-conserving surgery, known as lumpectomy, followed by radiation therapy.
Breast removal surgery, known as mastectomy.

In some cases, treatment may also include only a lumpectomy, a lumpectomy combined with hormone therapy, and joining a clinical trial to undertake treatments that might still be under trial.

Conclusion

There are many types of breast cancer, and the exact type you have will be determined after your initial diagnosis of cancer. While there are certain risk factors for breast cancer that are not under anyone’s control, but by following a healthy lifestyle, going for regular breast screenings, eating a nutritious and well-balanced diet, and exercising regularly can help reduce your risk of getting breast cancer.

References:

Key, T.J., Verkasalo, P.K. and Banks, E., 2001. Epidemiology of breast cancer. The lancet oncology, 2(3), pp.133-140.
Lo, P.K. and Sukumar, S., 2008. Epigenomics and breast cancer.
Elmore, J.G., Armstrong, K., Lehman, C.D. and Fletcher, S.W., 2005. Screening for breast cancer. Jama, 293(10), pp.1245-1256.
Welch, D.R., Steeg, P.S. and Rinker-Schaeffer, C.W., 2000. Molecular biology of breast cancer metastasis Genetic regulation of human breast carcinoma metastasis. Breast Cancer Research, 2(6), pp.1-9.
Keydar, I., Chen, L., Karby, S., Weiss, F.R., Delarea, J., Radu, M., Chaitcik, S. and Brenner, H.J., 1979. Establishment and characterization of a cell line of human breast carcinoma origin. European Journal of Cancer (1965), 15(5), pp.659-670.
Espina, V. and Liotta, L.A., 2011. What is the malignant nature of human ductal carcinoma in situ?. Nature Reviews Cancer, 11(1), pp.68-75.
Caldefie-Chezet, F., Damez, M., De Latour, M., Konska, G., Mishellani, F., Fusillier, C., Guerry, M., Penault-Llorca, F., Guillot, J. and Vasson, M.P., 2005. Leptin: a proliferative factor for breast cancer?: Study on human ductal carcinoma. Biochemical and biophysical research communications, 334(3), pp.737-741.
Brown, D.D., Dabbs, D.J., Lee, A.V., McGuire, K.P., Ahrendt, G.M., Bhargava, R., Davidson, N.E., Brufsky, A.M., Johnson, R.R., Oesterreich, S. and McAuliffe, P.F., 2015. Developing in vitro models of human ductal carcinoma in situ from primary tissue explants. Breast cancer research and treatment, 153(2), pp.311-321.
Borst, M.J. and Ingold, J.A., 1993. Metastatic patterns of invasive lobular versus invasive ductal carcinoma of the breast. Surgery, 114(4), pp.637-642.
Toikkanen, S., Pylkkänen, L. and Joensuu, H., 1997. Invasive lobular carcinoma of the breast has better short-and long-term survival than invasive ductal carcinoma. British journal of cancer, 76(9), pp.1234-1240.
Martinez, V. and Azzopardi, J.G., 1979. Invasive lobular carcinoma of the breast: incidence and variants. Histopathology, 3(6), pp.467-488.
Reed, A.E.M., Kutasovic, J.R., Lakhani, S.R. and Simpson, P.T., 2015. Invasive lobular carcinoma of the breast: morphology, biomarkers and’omics. Breast cancer research, 17(1), pp.1-11.
Page, D.L., Dixon, J.M., Anderson, T.J., Lee, D. and Stewart, H.J., 1983. Invasive cribriform carcinoma of the breast. Histopathology, 7(4), pp.525-536.
Venable, J.G., Schwartz, A.M. and Silverberg, S.G., 1990. Infiltrating cribriform carcinoma of the breast: a distinctive clinicopathologic entity. Human pathology, 21(3), pp.333-338.
Ridolfi, R.L., Rosen, P.P., Port, A., Kinne, D. and Miké, V., 1977. Medullary carcinoma of the breast. A clinicopathologic study with 10 year follow‐up. Cancer, 40(4), pp.1365-1385.
Meyer, J.E., Amin, E., Lindfors, K.K., Lipman, J.C., Stomper, P.C. and Genest, D., 1989. Medullary carcinoma of the breast: mammographic and US appearance. Radiology, 170(1), pp.79-82.
Lacroix‐Triki, M., Suarez, P.H., MacKay, A., Lambros, M.B., Natrajan, R., Savage, K., Geyer, F.C., Weigelt, B., Ashworth, A. and Reis‐Filho, J.S., 2010. Mucinous carcinoma of the breast is genomically distinct from invasive ductal carcinomas of no special type. The Journal of pathology, 222(3), pp.282-298.
Lam, W.W.M., Chu, W.C.W., Tse, G.M. and Ma, T.K., 2004. Sonographic appearance of mucinous carcinoma of the breast. American Journal of Roentgenology, 182(4), pp.1069-1074.
Pal, S.K., Lau, S.K., Kruper, L., Nwoye, U., Garberoglio, C., Gupta, R.K., Paz, B., Vora, L., Guzman, E., Artinyan, A. and Somlo, G., 2010. Papillary carcinoma of the breast: an overview. Breast cancer research and treatment, 122(3), pp.637-645.
Saremian, J. and Rosa, M., 2012. Solid papillary carcinoma of the breast: a pathologically and clinically distinct breast tumor. Archives of Pathology & Laboratory Medicine, 136(10), pp.1308-1311.
Rakha, E.A., Lee, A.H., Evans, A.J., Menon, S., Assad, N.Y., Hodi, Z., Macmillan, D., Blamey, R.W. and Ellis, I.O., 2010. Tubular carcinoma of the breast: further evidence to support its excellent prognosis. Journal of clinical oncology, 28(1), pp.99-104.
Sullivan, T., Raad, R.A., Goldberg, S., Assaad, S.I., Gadd, M., Smith, B.L., Powell, S.N. and Taghian, A.G., 2005. Tubular carcinoma of the breast: a retrospective analysis and review of the literature. Breast cancer research and treatment, 93(3), pp.199-205.
Jaiyesimi, I.A., Buzdar, A.U. and Hortobagyi, G., 1992. Inflammatory breast cancer: a review. Journal of clinical oncology, 10(6), pp.1014-1024.
Robertson, F.M., Bondy, M., Yang, W., Yamauchi, H., Wiggins, S., Kamrudin, S., Krishnamurthy, S., Le‐Petross, H., Bidaut, L., Player, A.N. and Barsky, S.H., 2010. Inflammatory breast cancer: the disease, the biology, the treatment. CA: a cancer journal for clinicians, 60(6), pp.351-375.
Peart, O., 2017. Metastatic breast cancer. Radiologic technology, 88(5), pp.519M-539M.
Jones, S.E., 2008. Metastatic breast cancer: the treatment challenge. Clinical breast cancer, 8(3), pp.224-233.
Chen, K.T., Kirkegaard, D.D. and Bocian, J.J., 1980. Angiosarcoma of the breast. Cancer, 46(2), pp.368-371.
Dixon, A.R., Galea, M.H., Ellis, I.O., Elston, C.W. and Blamey, R.W., 1991. Paget’s disease of the nipple. Journal of British Surgery, 78(6), pp.722-723.
Belkacémi, Y., Bousquet, G., Marsiglia, H., Ray-Coquard, I., Magné, N., Malard, Y., Lacroix, M., Gutierrez, C., Senkus, E., Christie, D. and Drumea, K., 2008. Phyllodes tumor of the breast. International Journal of Radiation Oncology* Biology* Physics, 70(2), pp.492-500.
Loibl, S. and Gianni, L., 2017. HER2-positive breast cancer. The Lancet, 389(10087), pp.2415-2429.
Engel, R.H. and Kaklamani, V.G., 2007. HER2-positive breast cancer. Drugs, 67(9), pp.1329-1341.
Foulkes, W.D., Smith, I.E. and Reis-Filho, J.S., 2010. Triple-negative breast cancer. New England journal of medicine, 363(20), pp.1938-1948.
Irvin Jr, W.J. and Carey, L.A., 2008. What is triple-negative breast cancer?. European journal of cancer, 44(18), pp.2799-2805.

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Types of Breast Cancer and What Type of Breast Cancer is Most Curable?