Cancer tissue has a distinctive appearance under the microscope. Among the distinguishing traits are a large number of dividing cells, variation in nuclear size and shape, variation in cell size and shape, loss of specialized cell features, loss of normal tissue organization, and a poorly defined tumor boundary. Immunohistochemistry and other molecular methods may characterise specific markers on tumor cells, which may aid in diagnosis and prognosis. Read the rest of this entry »

Physical carcinogens

Cancer pathogenesis is traceable back to DNA mutations that impact cell growth and metastasis. Substances that cause DNA mutations are known as mutagens, and mutagens that cause cancers are known as carcinogens. Particular substances have been linked to specific types of cancer. Tobacco smoking is associated with lung cancer and bladder cancer. Prolonged exposure to radiation, particularly ultraviolet radiation from the sun, leads to melanoma and other skin malignancies. Breathing asbestos fibers is associated with mesothelioma. Read the rest of this entry »

Aneuploidy

Down syndrome patients, who have an extra Chromosome 21, are known to develop malignancies such as leukemia and testicular cancer, though the reasons for this difference are not well understood. Characteristic changes in the copy number of particular chromosomes and chromosomal segments are seen in acute myeloid leukemia. These changes are so well-defined that they are used for prognostication in acute myeloid leukemia. Read the rest of this entry »

Tumor suppressor genes code for anti-proliferation signals and proteins that suppress mitosis and cell growth. Generally, tumor suppressors are transcription factors that are activated by cellular stress or DNA damage. Often DNA damage will cause the presence of free-floating genetic material as well as other signs, and will trigger enzymes and pathways which lead to the activation of tumor suppressor genes. The functions of such genes is to arrest the progression of the cell cycle in order to carry out DNA repair, preventing mutations from being passed on to daughter cells. The p53 protein, one of the most important studied tumor suppressor gene, is a transcription factor activated by many cellular stressors including hypoxia and ultraviolet radiation damage. Read the rest of this entry »

A few types of cancer in non-humans have been found to be caused by the tumor cells themselves. This phenomenon is seen in Sticker’s sarcoma, also known as canine transmissible venereal tumor.[7] The closest known analogue to this in humans is individuals who have developed cancer from tumors hiding inside organ transplants.

 Molecular biology

Cancers are caused by a series of mutations. Each mutation alters the behavior of the cell somewhat.

 Carcinogenesis, which means the initiation or generation of cancer, is the process of derangement of the rate of cell division due to perturbations in normal cellular regulatory processes. Molecular biology, the study of genetics using modern techniques such as gene cloning, seeks to explain the etiology of cancer in terms of the genetic changes that underlie cancer. Read the rest of this entry »

Main article: Carcinogenesis

 Origins of cancer

 The origin, or etiology of cancer can be approached from many different perspectives. What follows below is a summary of several different lines of scientific inquiry into the cause of cancer. One or all of these theories may explain the development of any given cancer.

 Cell dynamic theories

 Cell division or cell proliferation is a physiological process that occurs in almost all tissues and under many circumstances. Normally the balance between proliferation and apoptosis, or programmed cell death, is tightly regulated to ensure the integrity of organs and tissues. Imbalances in the rates of cell division and Read the rest of this entry »

Adult cancers

In the USA and other developed countries, cancer is presently responsible for about 25% of all deaths.[4] On a yearly basis, 0.5% of the population is diagnosed with cancer.

The statistics below are for adults in the United States, and will vary substantially in other countries:

Male                   ÂÂ

most common      cause of death[4] ÂÂ

prostate cancer (33%)                lung cancer (31%)             ÂÂ

lung cancer (13%)                      prostate cancer (10%)        Read the rest of this entry »

Nomenclature and classification

The following closely related terms may be used to designate abnormal growths:

* Neoplasia and neoplasm are scientific terms which refer to abnormal proliferations of genetically altered cells.

* Cancer is synonymous with malignant neoplasm.

* Benign tumors or benign neoplasms are similar to cancers in that they are composed of genetically abnormal cells which grow in excess of any normal process. However, the growth of benign tumors is self-limiting, and they do not invade other tissues or metastasize.

* Tumor originally referred to any swelling or mass, either neoplastic, inflammatory or other. However, the vast majority of entities referred to as tumors in common usage are in fact neoplasms (although many are benign, and thus not cancers).

* A paraneoplastic phenomenon is a physiological disturbance associated with a neoplasm, but not related to the physical effects of a tumor mass or invasive tumor cells themselves. Disturbances can be hormonal, neurological, hematological, or biochemical. Read the rest of this entry »

Hippocrates described several kinds of cancers. He called benign tumours oncos, Greek for swelling, and malignant tumours carcinos, Greek for crab or crayfish. This name probably comes from the appearance of the cut surface of a solid malignant tumour, with a roundish hard center surrounded by pointy projections, vaguely resembling the shape of a crab (see photo). He later added the suffix -oma, Greek for swelling, giving the name carcinoma. Since it was against Greek tradition to open the body, Hippocrates only described and made drawings of outwardly visible tumors on the skin, nose, and breasts. Treatment was based on the humor theory of four bodily fluids (black and yellow bile, blood, and phlegm). According to the patient’s humor, treatment consisted of diet, blood-letting, and/or laxatives. Through the centuries it was discovered that cancer could occur anywhere in the body, but humor-theory based treatment remained popular until the 19th century with the discovery of cells. Read the rest of this entry »

Cancer is a disease characterized by disorderly division of cells, combined with the malignant behavior of these cells. Malignant cancer cells tend to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (the process whereby cancer cells can move through the bloodstream or lymphatic system to distant locations). Cancer may affect people at all ages, but risk tends to increase with age. It is one of the principal causes of death in developed countries.

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