Cancer

Cancer

Types of Cancer

There are hundreds of different types of cancer, but cancers in general, belong to five basic categories:

  • Carcinomas
  • Sarcomas
  • Myelomas
  • Lymphomas
  • Leukemias

Carcinomas are the most common cancers. They originate in tissues which either cover surfaces or line internal organs, accounting for 80 to 90 percent of malignant cases. There are two major subtypes of carcinoma:

  • Adenocarcinoma – develops in an organ or gland.
  • Squamous cell carcinoma - originates in the epithelium (surface layer of cells), usually the skin.

Examples of carcinomas include cancers of the breast (see figure below, Mammary ductal carcinoma), prostate, lung, intestine, skin (see figure below, squamous-cell carcinoma), pancreas, liver, kidneys, and bladder.

Mammary Ductal Carcinoma

Squamous Cell Carcinoma

Sarcomas are malignancies originating in connective tissue developing in bones, muscles, fat, cartilage, nerves, tendons, and joints, usually in the arms or legs. Sarcomas are the rarest and mostly deadly forms of cancer.

Myelomas are also rare forms of cancer and originates in the plasma cells of the bone marrow (soft tissue inside the bones). Plasma cells are immune cells responsible for fighting infection by producing antibodies. Myeloma cells hinder normal antibody production, weakening the immune system.

The increased rate of myeloma cell division additionally interferes with normal production and function of red and white cells and can result in bone destruction, leading to bone pain and/or fractures. Since myeloma often develops at many sites in the bone marrow, it is often called multiple myeloma.

Lymphomas are cancers that develop from lymphatic cells (a vital part of the immune system). The two most common types are Hodgkin disease and Non-Hodgkin lymphoma. The second group includes Common B-cell lymphoma and the rarer T-cell lymphoma. Non-Hodgkin lymphoma are also classified as indolent or aggressive, based on how fast they are growing.

Leukemias are cancers of the blood. The malignant cells begin to form in the bone marrow, the soft tissue inside nearly all of the bones. Bone marrow contains the cells that give rise to the following blood cells:

  • White blood cells (WBC) – enable your body to fight infection.
  • Red blood cells (RBC) – transport oxygen to all parts of the body.
  • Platelets – are important cells for blood clotting.

Once an individual has leukemia, his bone marrow starts to produce a great number of abnormal (malignant) WBCs, called leukemic cells. These cell don’t function like normal WBCs. They grow faster and don’t stop growing when they should.

With time, leukemic cells can crowd out the normal blood cells (see figure below). This can give rise to serious problems like anemia, bleeding, and infections. Leukemia cells can also metastasize to the lymph nodes or other organs and can result in swelling or pain.

Leukemia Cells

There are many types of leukemia. Generally, leukemia is identified by how rapidly it gets worse and what type of white blood cells are affected.

It can be acute or chronic. Acute leukemia gets worse very fast and symptoms appear quickly. Chronic leukemia gets worse gradually and will possibly not cause symptoms for years.

It could be lymphocytic or myelogenous. Lymphocytic leukemia involves white blood cells called lymphocytes. Myelogenous leukemia involves the other type of cells that give rise to granulocytes, red blood cells, or platelets.