Tumor

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. In other words, a tumor is a neoplasm where the abnormal growth of body tissue has resulted in a visual mass that appears enlarged in size.

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.

Terminology: Tumor, neoplasm, cancer

The terms tumor, neoplasm, and cancer are not synonymous, but do intersect.

Neoplasm is a medical term that refers to an abnormal proliferation of cells in contrast with healthy new cell growth and normal tissue. The growth of the cells exceeds and is uncoordinated with that of the normal tissues around it, resulting in an abnormal growth of tissue.

Tumor is the term for an abnormal lump of tissue formed by a neoplasm. However, while neoplasms often cause a lump or tumor, a neoplasm does not always proceed to such a visual mass. For example, leukemia is a type of neoplasm that is characterized by an abnormal increase of immature white blood cells but does not form a lump.

Cancer is the term for a "malignant neoplasm." Cancer is characterized not only by the uncontrolled growth of cells (division beyond the normal limits), but also the ability of these abnormally dividing cells to spread from the original site, whether to adjacent tissues (invasion) or, in some cases, even to distant sites in the body (metastasis).

While the terms tumor, neoplasm, and cancer are often used interchangeably (all three involve a failure of cell division control), they are distinct. For one, cancers and neoplasms may not form a tumor (eg. leukemia). Secondly, cancers are malignant (tendency to become progressively worse) and characterized by the ability to spread from the original site (invasions and metastatis). Tumors and neoplasms may be malignant and capable of spreading (cancerous), but they also may be benign and not capable of invading into adjacent tissues or spreading to distant tissues. Tumors and neoplasms also may be pre-malignant (morphologically altered tissue in which cancer is more likely to occur). In other words, 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. 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 (Carson-Dewitt 2002).

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), with other forms of swelling often referred to merely as swellings.

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 . 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 .

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)

External links

• Skintumor.info gallery
• Cancer Control MTCC

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:

• Tumor  ^history

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

• History of "Tumor"

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