Cancer Types
Cancers are classified in two ways: by the type of tissue in which the cancer
originates (histological type) and by primary site, or the location in the body
where the cancer first developed. From a histological standpoint there are
hundreds of different cancers, which are grouped into five major categories:
Carcinoma, Sarcoma,
Myeloma, Leukemia, and
Lymphoma. In addition, there are also some cancers of
mixed types.
Medical processionals refer to cancers based on their histological
type, the rest of us are more familiar with cancer names based on
their primary sites. The most common sites in which cancer develops include the
skin, lungs, female breasts, prostate, colon and rectum, cervix and uterus.
Compared with those based on histological type, cancers named after the
primary site may not be as accurate. Saying that a woman has uterine carcinoma or
uterine cancer is the same thing as saying that she has cancer (or carcinoma) of
the uterus.
The most common types of cancers named for their
primary site are listed here.
There are three primary types of skin cancer: basal cell, squamous cell, and
melanoma. These cancers are derived from the epidermal layers with the same
names. Melanomas are derived from the melanocytes, or pigment cells, in the
deepest level of the epidermis.
Basal cell and squamous cell cancers usually occur on parts of the body
exposed to the sun, such as the face, ears, and extremities. These cancers
are highly curable, especially if detected and treated early. Melanomas form
dark moles that spread over the surface of the skin are more lethal because
they metastasize very quickly.
Lung cancer is very difficult to detect at an early stage because the
symptoms often do not appear until the disease has advanced. The symptoms
include persistent cough, sputum streaked with blood, chest pain, and repeated
attacks of pneumonia or bronchitis. Lung cancer, depending on how the
cells look under a microscope, can be non-small cell lung cancer and small cell
lung cancer. Non-small cell lung cancer can be further divided into various
types named for the type of cells in which the cancer develops, typically:
squamous cell carcinoma, adenocarcinoma, and large cell carcinoma.
Only 2% of breast cancers are in men. It has been estimated that in the U.S.,
about 1 in 8 women will eventually develop breast cancer in her life time. Most
breast cancers are ductal carcinomas. Statistically, women most likely to develop
breast cancer are over 50; have already had cancer in one breast; her mother or
sister had breast cancer; have never had children; or had her first child after
the age of 30. Other risk factors include being overweight; a high-fat diet;
early menarche (age menstruation begins) and late menopause (age menstruation ceases).
Breast self-examinations are recommended as a way to detect breast
cancer early. Most of the lumps found in the breasts are not cancerous,
but women should see their physicians to find out for sure. The American
Cancer Society also recommends periodic mammograms (or breast X-rays) for
all women over the age of 40, as well as physical examinations of the
breast by a physician for all women over the age of 20, even if they have
no symptoms of breast cancer.
Cancer of the prostate is found mainly in older men. As men age, the prostate
may enlarge and block the urethra or bladder. This may cause difficulty in
urination or interfere with sexual functions. This condition is called benign
prostatic hypertrophy (BPH). Although BPH is not cancerous, it should be
corrected. Beta sitosterol found in saw palmetto berries has been found to be
very effective. The symptoms of BPH, or of other problems in the prostate,
may be similar to symptoms for prostate cancer.
Consult a physician if any of the following symptoms appear: weak or interrupted
flow of urine; urinating often (especially at night); difficulty urinating; pain
or burning during urination; blood in the urine; or nagging pain in the back, hips,
or pelvis. Often there are no symptoms of early cancer of the prostate.
Colorectal cancers affect the large intestine, about 70 percent occur in the
colon and about 30 percent in the rectum. These cancers are the third most
common cancers overall. Symptoms include blood in the stool which can be tested
for by a simple fecal occult blood test) or a change in bowel habits, such as
severe constipation or diarrhea.
Together with cancer of the cervix, cancer of the uterus is the most common
gynecologic malignancy. This cancer occurs infrequently in women under 40 years
of age. It occurs most frequently after the age of 60. The presenting symptom is
usually abnormal uterine bleeding. 10-25 percent of malignancies occur in
women who received pelvic radiation five to 25 years earlier for benign bleeding.
As in other cancers of its type, risk factors for uterine cancer include diabetes,
hypertension, obesity, and improper estrogen levels.
In addition to cancer types named after the primary site discussed above,
there are many other examples such as brain cancer, testicular cancer, bladder
cancer, and so on.
Carcinoma refers to a malignant neoplasm of epithelial origin or cancer of
the internal or external lining of the body. Carcinomas, malignancies of
epithelial tissue, account for 80 to 90 percent of all cancer cases.
Epithelial tissue is found throughout the body. It is present in the skin, as
well as the covering and lining of organs and internal passageways, such as the
gastrointestinal tract.
Carcinomas are divided into two major subtypes: adenocarcinoma, which
develops in an organ or gland, and squamous cell carcinoma, which originates in
the squamous epithelium.
Adenocarcinomas generally occur in mucus membranes and are first seen as a
thickened plaque-like white mucosa. They often spread easily through the soft
tissue where they occur. Squamous cell carcinomas occur in many areas of the
body.
Most carcinomas affect organs or glands capable of secretion, such as the
breasts, which produce milk, or the lungs, which secrete mucus, or colon or
prostate or bladder.
Sarcoma refers to cancer that originates in supportive and connective tissues
such as bones, tendons, cartilage, muscle, and fat. Generally occurring in young
adults, the most common sarcoma often develops as a painful mass on the bone.
Sarcoma tumors usually resemble the tissue in which they grow.
Examples of sarcomas are:
- Osteosarcoma or osteogenic sarcoma (bone)
- Chondrosarcoma (cartilage)
- Leiomyosarcoma (smooth muscle)
- Rhabdomyosarcoma (skeletal muscle)
- Mesothelial sarcoma or mesothelioma (membranous lining of body cavities)
- Fibrosarcoma (fibrous tissue)
- Angiosarcoma or hemangioendothelioma (blood vessels)
- Liposarcoma (adipose tissue)
- Glioma or astrocytoma (neurogenic connective tissue found in the brain)
- Myxosarcoma (primitive embryonic connective tissue)
- Mesenchymous or mixed mesodermal tumor (mixed connective tissue types)
Myeloma is cancer that originates in the plasma cells of bone marrow. The
plasma cells produce some of the proteins found in blood.
Leukemias ("liquid cancers" or "blood cancers") are cancers
of the bone marrow (the site of blood cell production). The word leukemia means
"white blood" in Greek. The disease is often associated with the
overproduction of immature white blood cells. These immature white blood cells do
not perform as well as they should, therefore the patient is often prone to
infection. Leukemia also affects red blood cells and can cause poor blood clotting
and fatigue due to anemia. Examples of leukemia include:
- Myelogenous or granulocytic leukemia (malignancy of the myeloid and
granulocytic white blood cell series)
- Lymphatic, lymphocytic, or lymphoblastic leukemia (malignancy of the
lymphoid and lymphocytic blood cell series)
- Polycythemia vera or erythremia (malignancy of various blood cell
products, but with red cells predominating)
Lymphomas develop in the glands or nodes of the lymphatic system, a network
of vessels, nodes, and organs (specifically the spleen, tonsils, and thymus)
that purify bodily fluids and produce infection-fighting white blood cells, or
lymphocytes. Unlike the leukemias which are sometimes called "liquid cancers,"
lymphomas are "solid cancers." Lymphomas may also occur in specific organs such
as the stomach, breast or brain. These lymphomas are referred to as extranodal
lymphomas. The lymphomas are subclassified into two categories: Hodgkin lymphoma
and Non-Hodgkin lymphoma. The presence of Reed-Sternberg cells in Hodgkin lymphoma
diagnostically distinguishes Hodgkin lymphoma from Non-Hodgkin lymphoma.
Mixed Types
The type components may be within one category or from different categories.
Some examples are:
- adenosquamous carcinoma
- mixed mesodermal tumor
- carcinosarcoma
- teratocarcinoma
Lymphoma is a cancer of the lymphatic system - the network of lymph
glands and channels which occurs throughout the body. There are thirty-five different
types of lymphoma recognised in the most recent classification system. These are grouped
into two main types called Hodgkin's disease (five sub-types), and non-Hodgkin's lymphoma (thirty
sub-types). Hodgkin's disease (HD) is distinguished from all other types of lymphoma by the
presence of a distinctive abnormal lymphocyte called a Reed-Sternberg cell. All types of
lymphoma except Hodgkin's disease are collectively known as non-Hodgkin's lymphoma (NHL). The
Editorial Committee of the International Classification of Diseases for Oncology, Third Edition,
adopted the European eponymic standard, which is to drop the apostrophy 's' on eponyms
(such as Hodgkin's ). Therefore, the medical community is learning to refer to Hodgkin's
disease as Hodgkin disease (and Hodgkin lymphoma) and Non-Hodgkin's lymphoma as Non-Hodgkin lymphoma.
|
