Tumor

From New World Encyclopedia
Revision as of 18:29, 3 March 2012 by Rick Swarts (talk | contribs)
Neoplastic tumor of the cheek skin, here a benign neoplasm of the sweat glands called Hidradenoma, which is not solid but is fluid-filled.

Tumor (or "tumour") is the term for an abnormal growth of cells (neoplasm) that has formed a lump, whether benign (noncancerous), malignant (cancerous), pre-malignant, or without any cancerous potential whatsoever.

abnormal growth of body tissue. Tumors can be cancerous (malignant) or noncancerous (benign).

commonly used as a synonym for a neoplasm (a solid or fluid-filled (cystic) lesion that may or may not be formed by an abnormal growth of neoplastic cells) that appears enlarged in size.[1] Tumor is not synonymous with cancer. While cancer is by definition malignant, a tumor can be benign, pre-malignant, or malignant, or can represent a lesion without any cancerous potential whatsoever.

Notes:

Cancer, or "malignant neoplasm," is a large category of almost one hundred diseases, characterized by uncontrolled growth of cells and the ability of these abnormally dividing cells to spread from the original site, whether to adjacent tissues or, in some cases, even to distant sites in the body. Known as "a disease of the genes," some cancers have an hereditary basis whereby an individual inherits faulty DNA from his or her parents, perhaps due to an error in replication of the DNA. However, most types of cancers originate from changes to a cell's DNA (mutations) due to environmental factors (carcinogens), such as tobacco smoke, UV radiation, chemicals, or infectious agents.

If the spread of cancer is not controlled, it can result in death, and cancer is one of the leading causes of death worldwide. The risk of cancer increases with age, with most cases occurring in people older than 65 years of age. Among well-known cancers are skin cancer, breast cancer (in women), prostate cancer (in men), colon cancer, and lung cancer. The branch of medicine concerned with the study, diagnosis, treatment, and prevention of cancer is oncology.

The terms cancer and tumor are not synonymous. In modern medicine, the term cancer is interchangeable with the term malignant neoplasm. A neoplasm is an abnormal overgrowth of cells; a tumor is a neoplasm that has formed a lump. However, neoplasms and tumors may be benign or they may be malignant. A benign tumor or benign neoplasm does not spread or migrate to surrounding tissues; thus, it is not considered cancer. The malignant versions do involve the invasion of surrounding tissues and perhaps the spreading to other parts of the body; thus, a malignant tumor or malignant neoplasm is cancer. Some cancers, however, do not form a tumor, such as leukemia.


Cancer is a class of diseases in which a group of cells display uncontrolled growth (division beyond the normal limits), invasion (intrusion on and destruction of adjacent tissues), and sometimes metastasis (spread to other locations in the body via lymph or blood).

Cancer has been called "a disease of cell division—a failure of cell division control."[2] Cancerous cells undergo uncontrolled cell division.

The three properties of cancers (uncontrolled growth, invasion, and metastasis) differentiate them from benign tumors and benign neoplasms.

Neoplasm is a medical term that refers to a new growth of cells. Whereas "neo" means new and "plasm" refers to cells, the word neoplasm refers to ab abnormal overgrowth of cells rather than healthy new cell growth. Neoplasm is an abnormal mass of tissue as a result of neoplasia (the abnormal proliferation of cells). The growth of the cells exceeds, and is uncoordinated with that of the normal tissues around it. The growth persists in the same excessive manner even after cessation of the stimuli. It usually causes a lump or tumor.

Neoplasm is often used interchangeably with words such as tumor and cancer. However, neoplasms may be benign, pre-malignant or malignant. Likewise, tumors—a neoplasm that has formed a lump—may be benign, pre-malignant, or malignant. Cancer, whether forming or tumor or not, is malignant. Cancer involves both "uncontrolled growth" and "invasion," and sometimes "metastasis," whereas a benign neoplasm or benign tumor is self-limited, and does not invade or metastasize. Furthermore, the removal of a benign tumor usually prevents the re-occurrence of the condition, whereas if the cancer has spread to surrounding tissues, the removal of a malignant tumor does not prevent the re-occurrence of the cancer.[3] The main use of the term neoplasm is in medical statistics that categorize deaths or other events, in which case neoplasm is typically the category that includes cancer statistics.


Etymology

The term tumour/tumor is derived from the Latin word for "swelling" — tumor. It is similar to the Old French tumour (contemporary French: tumeur). In the Commonwealth the spelling "tumour" is commonly used, whereas in the U.S. it is usually spelled "tumor".

In its medical sense it has traditionally meant an abnormal swelling of the flesh. The Roman medical encyclopedist Celsus (ca 30 B.C.E.–38 C.E.) described the four cardinal signs of acute inflammation as tumor, dolor, calor, and rubor (swelling, pain, increased heat, and redness). His treatise, De Medicina, was the first medical book printed in 1478 following the invention of the movable-type printing press.

In contemporary English, the word tumor is often used as a synonym for a cystic (liquid-filled) growth or solid neoplasm (cancerous or non-cancerous),[4] with other forms of swelling often referred to merely as swellings.[5]

Related terms are common in the medical literature, where the nouns tumefaction and tumescence (derived from the adjective tumefied), are current medical terms for non-neoplastic swelling. This type of swelling is most often caused by inflammation caused by trauma, infection, and other factors..etc.

Tumors may be caused by conditions other than an overgrowth of neoplastic cells, however. Cysts (such as sebaceous cysts) are also referred to as tumors, even though they have no neoplastic cells. This is standard in medical billing terminology (especially when billing for a growth whose pathology has yet to be determined)..

Causes

A neoplasm can be caused by an abnormal proliferation of tissues, which can be caused by genetic mutations. Not all types of neoplasms cause a tumorous overgrowth of tissue, however (such as leukemia or carcinoma in situ).

Recently, tumor growth has been studied using mathematics and continuum mechanics. Vascular tumors are thus looked at as being amalgams of a solid skeleton formed by sticky cells and an organic liquid filling the spaces in which cells can grow [6] . Under this type of model, mechanical stresses and strains can be dealt with and their influence on the growth of the tumor and the surrounding tissue and vasculature elucidated. Recent findings from experiments that use this model show, among other things, that active growth of the tumor is restricted to the outer edges of the tumor, and that stiffening of the underlying normal tissue inhibits tumor growth as well [7].

Benign conditions that are not associated with an abnormal proliferation of tissue (such as sebaceous cysts) can also present as tumors, however, but have no malignant potential. Breast cysts (as occur commonly during pregnancy and at other times) are another example, as are other encapsulated glandular swellings (thyroid, adrenal gland, pancreas).

Encapsulated hematomas, encapsulated necrotic tissue (from an insect bite, foreign body, or other noxious mechanism), and keloids (discrete overgrowths of scar tissue) and granulomas may also present as tumors.

Discrete localized enlargements of normal structures (ureters, blood vessels, intrahepatic or extrahepatic biliary ducts, pulmonary inclusions, or gastrointestinal duplications) due to outflow obstructions or narrowings, or abnormal connections, may also present as a tumor. Examples are arteriovenous fistulae or aneurysms (with or without thrombosis), biliary fistulae or aneurysms, sclerosing cholangitis, cysticercosis or hydatid cysts, intestinal duplications, and pulmonary inclusions as seen with cystic fibrosis. It can be dangerous to biopsy a number of types of tumor in which the leakage of their contents would potentially be catastrophic. When such types of tumors are encountered, diagnostic modalities such as ultrasound, CT scans, MRI, angiograms, and nuclear medicine scans are employed prior to (or during) biopsy and/or surgical exploration/excision in an attempt to avoid such severe complications.

The nature of a tumor is determined by imaging, by surgical exploration, and/or by a pathologist after examination of the tissue from a biopsy or a surgical specimen.

See also

  • Cancer
  • Neoplasm
  • History of Medicine
  • Swelling (medical)

References
ISBN links support NWE through referral fees

  1. Template:DorlandsDict
  2. P.H. Raven, G. B. Johnson, J.B. Raven, K. A. Mason, and S. R. Singer, Biology, 8th edition. (Boston: McGraw Hill 2008). ISBN 9780072965810.
  3. Cite error: Invalid <ref> tag; no text was provided for refs named Carson-DeWitt
  4. Tumor in MedlinePlus Medical Encyclopedia
  5. Swelling in MedlinePlus Medical Encyclopedia
  6. {{{title}}}.
  7. {{{title}}}.

External links

Tumors (and related structures), Cancer, and Oncology
Benign - Premalignant - Carcinoma in situ - Malignant

Topography: Anus - Bladder - Bone - Brain - Breast - Cervix - Colon/rectum - Duodenum - Endometrium - Esophagus - Eye - Gallbladder - Head/Neck - Liver - Larynx - Lung - Mouth - Pancreas - Penis - Prostate - Kidney - Ovaries - Skin - Stomach - Testicles - Thyroid

Morphology: Papilloma/carcinoma - Adenoma/adenocarcinoma - Soft tissue sarcoma - Melanoma - Fibroma/fibrosarcoma - Lipoma/liposarcoma - Leiomyoma/leiomyosarcoma - Rhabdomyoma/rhabdomyosarcoma - Mesothelioma - Angioma/angiosarcoma - Osteoma/osteosarcoma - Chondroma/chondrosarcoma - Glioma - Lymphoma/leukemia

Treatment: Chemotherapy - Radiation therapy - Immunotherapy - Experimental cancer treatment

Related structures: Cyst - Dysplasia - Hamartoma - Neoplasia - Nodule - Polyp - Pseudocyst

Misc: Tumor suppressor genes/oncogenes - Staging/grading - Carcinogenesis/metastasis - Carcinogen - Research - Paraneoplastic phenomenon - ICD-O - List of oncology-related terms


References

  • Kleinsmith, L. J. 2006. Principles of Cancer Biology. Pearson Benjamin Cummings. ISBN 0805340033.
  • Parkin, D., F. Bray, J. Ferlay, and P. Pisani. 2005. "Global cancer statistics, 2002," CA Cancer J Clin 55(2): 74–108. PMID 15761078. Retrieved September 9, 2010.}}
  • Schwab, M. (Ed.) 2009. Encyclopedia of Cancer. 4 volume reference work. Springer. ISBN: 9783540368472. Retrieved September 9, 2010.
  • Tannock, I. F., R. P. Hill, et al. (Eds.). 2005. The Basic Science of Oncology 4th ed. McGraw-Hill. ISBN 0071387749.

Credits

New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:

The history of this article since it was imported to New World Encyclopedia:

Note: Some restrictions may apply to use of individual images which are separately licensed.