View source for Medicine:Benign tumor

{{Short description|Mass of cells which cannot spread throughout the body}}
{{Infobox medical condition (new)
| name            = Benign tumor
| synonyms        = non-cancerous tumor
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| field           = [[Medicine:Oncology|Oncology]], [[Biology:Pathology|Pathology]]
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A '''benign tumor''' is a mass of [[Biology:Cell|cells]] (tumor) that does not invade neighboring tissue or [[Medicine:Metastasis|metastasize]] (spread throughout the body). Compared to [[Medicine:Cancer|malignant (cancerous) tumors]], benign tumors generally have a slower [[Biology:Cell growth|growth rate]]. Benign tumors have relatively well differentiated cells. They are often surrounded by an outer surface (fibrous sheath of connective tissue) or stay contained within the [[Biology:Epithelium|epithelium]]. Common examples of benign tumors include moles and [[Medicine:Uterine fibroid|uterine fibroid]]s.

Some forms of benign tumors may be harmful to health. Benign tumor growth causes a [[Medicine:Mass effect|mass effect]] that can compress neighboring tissues. This can lead to nerve damage, blood flow reduction (ischemia), tissue death ([[Biology:Necrosis|necrosis]]), or organ damage. The health effects of benign tumor growth may be more prominent if the tumor is contained within an enclosed space such as the cranium, [[Medicine:Respiratory tract|respiratory tract]], [[Biology:Sinus (anatomy)|sinus]], or bones. For example, unlike most benign tumors elsewhere in the body, benign [[Medicine:Brain tumor|brain tumor]]s can be life-threatening. Tumors may exhibit behaviors characteristic of their cell type of origin; as an example, endocrine tumors such as thyroid adenomas and adrenocortical adenomas may overproduce certain [[Biology:Hormone|hormone]]s.

The word "benign" means "favourable, kind, fortunate, salutary, propitious".<ref>{{Cite OED|Benign|id=17733}}</ref> However, a benign tumour is not ''benign'' in the usual sense; the name merely specifies that it is not "malignant", i.e. cancerous. While benign tumours usually do not pose a serious health risk, they can be harmful or fatal.<ref>{{Cite book |chapter=Overview of Heart Tumors - Treatment of noncancerous (benign) heart tumors | vauthors = Rao AK |title=MSD Manual Consumer Version |date=February 2021 |url= https://www.msdmanuals.com/en-gb/home/heart-and-blood-vessel-disorders/heart-tumors/overview-of-heart-tumors |quote=Children with this type of [inoperable, benign] tumor usually die of an abnormal heart rhythm at an early age. }}</ref> Many types of benign tumors have the potential to become cancerous ([[Medicine:Malignancy|malignant]]) through a process known as [[Biology:Tumor progression|tumor progression]]. For this reason and other possible harms, some benign tumors are removed by surgery. When removed, benign tumors usually do not return. Exceptions to this rule may indicate malignant transformation.

==Signs and symptoms==
Benign tumors are very diverse; they may be asymptomatic or may cause specific symptoms, depending on their anatomic location and tissue type. They grow outward, producing large, rounded masses which can cause what is known as a "mass effect". This growth can cause compression of local tissues or organs, leading to many effects, such as blockage of ducts, reduced blood flow (ischaemia), tissue death ([[Biology:Necrosis|necrosis]]) and nerve pain or damage.<ref name="ISBN 0-443-10101-9">{{cite book |title=Ross and Wilson anatomy and physiology in health and illness |vauthors=Wilson KA, Waugh A, Chambers G, Grant A, Ross J |publisher=Churchill Livingstone |year=2006 |isbn=0-443-10101-9 |location=Edinburgh |pages=53–54}}</ref> Some tumors also produce hormones that can lead to life-threatening situations. [[Medicine:Insulinoma|Insulinoma]]s can produce large amounts of insulin, causing [[Medicine:Hypoglycemia|hypoglycemia]].<ref name="pmid1665409">{{cite journal | vauthors = Marks V, Teale JD | title = Tumours producing hypoglycaemia | journal = Diabetes/Metabolism Reviews | volume = 7 | issue = 2 | pages = 79–91 | date = June 1991 | pmid = 1665409 | doi = 10.1002/dmr.5610070202 | s2cid = 19272145 }}</ref><ref name="pmid16253900">{{cite journal | vauthors = Grant CS | title = Insulinoma | journal = Best Practice & Research. Clinical Gastroenterology | volume = 19 | issue = 5 | pages = 783–798 | date = October 2005 | pmid = 16253900 | doi = 10.1016/j.bpg.2005.05.008 }}</ref> Pituitary adenomas can cause elevated levels of hormones such as [[Biology:Growth hormone|growth hormone]] and insulin-like growth factor-1, which cause [[Medicine:Acromegaly|acromegaly]]; [[Biology:Prolactin|prolactin]]; ACTH and [[Chemistry:Cortisol|cortisol]], which cause Cushing's disease; [[Biology:Thyroid-stimulating hormone|TSH]], which causes [[Medicine:Hyperthyroidism|hyperthyroidism]]; and [[Biology:Follicle-stimulating hormone|FSH]] and [[Biology:Luteinizing hormone|LH]].<ref name="ISBN 92-832-2416-7">{{cite book | vauthors = Eng C, DeLellis RA, Lloyd RV, Heitz PU |title=Pathology and genetics of tumours of endocrine organs|publisher=IARC Press |location=Lyon |year=2004 |isbn=92-832-2416-7 }}</ref> Bowel [[Medicine:Intussusception (medical disorder)|intussusception]] can occur with various benign colonic tumors.<ref name="pmid11588539">{{cite journal | vauthors = Gill SS, Heuman DM, Mihas AA | title = Small intestinal neoplasms | journal = Journal of Clinical Gastroenterology | volume = 33 | issue = 4 | pages = 267–282 | date = October 2001 | pmid = 11588539 | doi = 10.1097/00004836-200110000-00004 }}</ref> Cosmetic effects can be caused by tumors, especially those of the skin, possibly causing psychological or social discomfort for the person with the tumor.<ref name="pmid15953143">{{cite journal | vauthors = Tromberg J, Bauer B, Benvenuto-Andrade C, Marghoob AA | title = Congenital melanocytic nevi needing treatment | journal = Dermatologic Therapy | volume = 18 | issue = 2 | pages = 136–150 | year = 2005 | pmid = 15953143 | doi = 10.1111/j.1529-8019.2005.05012.x | s2cid = 20915929 | doi-access = free }}</ref> [[Medicine:Vascular tumor|Vascular tissue tumors]] can bleed, in some cases leading to [[Medicine:Anemia|anemia]].<ref name = "zuberandharder1">{{cite book| vauthors = Zuber M, Harder F |title=Benign tumors of the colon and rectum|year=2001|publisher=Surgical Treatment: Evidence-Based and Problem-Oriented.|location=Munich: Zuckschwerdt|url=https://www.ncbi.nlm.nih.gov/books/NBK6994/}}</ref>

==Causes==

=== PTEN hamartoma syndrome ===
PTEN hamartoma syndrome encompasses [[Medicine:Hamartoma|hamartoma]]tous disorders characterized by genetic mutations in the [[Biology:PTEN (gene)|PTEN]] tumor suppressor gene,<ref>{{cite journal | vauthors = Pilarski R | title = ''PTEN'' Hamartoma Tumor Syndrome: A Clinical Overview | journal = Cancers | volume = 11 | issue = 6 | pages = 844 | date = June 2019 | pmid = 31216739 | pmc = 6627214 | doi = 10.3390/cancers11060844 | doi-access = free }}</ref> including [[Medicine:Cowden syndrome|Cowden syndrome]], [[Medicine:Bannayan–Riley–Ruvalcaba syndrome|Bannayan–Riley–Ruvalcaba syndrome]], [[Medicine:Proteus syndrome|Proteus syndrome]] and [[Medicine:Proteus-like syndrome|Proteus-like syndrome]]. Absent or dysfunctional PTEN protein allows cells to over-proliferate, causing hamartomas.<ref name="pmid196680822">{{cite journal |vauthors=Hobert JA, Eng C |date=October 2009 |title=PTEN hamartoma tumor syndrome: an overview |journal=Genetics in Medicine |volume=11 |issue=10 |pages=687–694 |doi=10.1097/GIM.0b013e3181ac9aea |pmid=19668082 |doi-access=free}}</ref> [[Medicine:Cowden syndrome|Cowden syndrome]] is an autosomal dominant [[Medicine:Genetic disorder|genetic disorder]] characterized by multiple benign [[Medicine:Hamartoma|hamartoma]]s (trichilemmomas and mucocutaneous papillomatous papules) as well as a predisposition for cancers of multiple organs including the breast and thyroid.<ref name="pmid151217672">{{cite journal |vauthors=Pilarski R, Eng C |date=May 2004 |title=Will the real Cowden syndrome please stand up (again)? Expanding mutational and clinical spectra of the PTEN hamartoma tumour syndrome |journal=Journal of Medical Genetics |volume=41 |issue=5 |pages=323–326 |doi=10.1136/jmg.2004.018036 |pmc=1735782 |pmid=15121767}}</ref><ref name="pmid110735352">{{cite journal |vauthors=Eng C |date=November 2000 |title=Will the real Cowden syndrome please stand up: revised diagnostic criteria |journal=Journal of Medical Genetics |volume=37 |issue=11 |pages=828–830 |doi=10.1136/jmg.37.11.828 |pmc=1734465 |pmid=11073535}}</ref> [[Medicine:Bannayan–Riley–Ruvalcaba syndrome|Bannayan–Riley–Ruvalcaba syndrome]] is a congenital disorder characterized by hamartomatous intestinal polyposis, macrocephaly, lipomatosis, hemangiomatosis and glans penis macules.<ref name="pmid196680822" /><ref name="pmid129380832">{{cite journal |vauthors=Eng C |date=September 2003 |title=PTEN: one gene, many syndromes |journal=Human Mutation |volume=22 |issue=3 |pages=183–198 |doi=10.1002/humu.10257 |pmid=12938083 |s2cid=13417857|doi-access=free }}</ref> [[Medicine:Proteus syndrome|Proteus syndrome]] is characterized by nevi, asymmetric overgrowth of various body parts, adipose tissue dysregulation, cystadenomas, [[Medicine:Adenoma|adenoma]]s, vascular malformation.<ref name="pmid187811912">{{cite journal |vauthors=Blumenthal GM, Dennis PA |date=November 2008 |title=PTEN hamartoma tumor syndromes |journal=European Journal of Human Genetics |volume=16 |issue=11 |pages=1289–1300 |doi=10.1038/ejhg.2008.162 |pmc=6939673 |pmid=18781191}}</ref><ref name="pmid160106812">{{cite journal |vauthors=Cohen MM |date=August 2005 |title=Proteus syndrome: an update |journal=American Journal of Medical Genetics. Part C, Seminars in Medical Genetics |volume=137C |issue=1 |pages=38–52 |doi=10.1002/ajmg.c.30063 |pmid=16010681 |s2cid=31873101|doi-access=free }}</ref>

[[File:Familial adenomatous polyposis as seen on sigmoidoscopy.jpg|thumb|left|Endoscopic image of sigmoid colon of a patient with familial adenomatous polyposis.]]

===Familial adenomatous polyposis===

Familial adenomatous polyposis (FAP) is a familial [[Medicine:Cancer syndrome|cancer syndrome]] caused by mutations in the [[Biology:Adenomatous polyposis coli|APC]] gene. In FAP, [[Medicine:Adenoma|adenoma]]tous polyps are present in the colon. The polyps progress into colon cancer unless removed.<ref name="pmid164548482">{{cite journal |vauthors=Galiatsatos P, Foulkes WD |date=February 2006 |title=Familial adenomatous polyposis |journal=The American Journal of Gastroenterology |volume=101 |issue=2 |pages=385–398 |doi=10.1111/j.1572-0241.2006.00375.x |pmid=16454848|s2cid=8516051 }}</ref> The APC gene is a [[Biology:Tumor suppressor|tumor suppressor]]. Its protein product is involved in many cellular processes. Inactivation of the APC gene leads to the buildup of a protein called β-catenin. This protein activates two transcription factors: T-cell factor (TCF) and [[Biology:Lymphoid enhancer-binding factor 1|lymphoid enhancer factor]] (LEF). These factors cause the upregulation of many genes involved in cell [[Biology:Cell growth|proliferation]], [[Biology:Cellular differentiation|differentiation]], [[Biology:Cell migration|migration]] and [[Biology:Apoptosis|apoptosis]] (programmed cell death), causing the growth of benign tumors.<ref name="pmid178814942">{{cite journal |vauthors=Aoki K, Taketo MM |date=October 2007 |title=Adenomatous polyposis coli (APC): a multi-functional tumor suppressor gene |journal=Journal of Cell Science |volume=120 |issue=Pt 19 |pages=3327–3335 |doi=10.1242/jcs.03485 |pmid=17881494 |doi-access= |s2cid=8743}}</ref>

===Tuberous sclerosis complex===
Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disorder caused by mutations in the genes TSC1 and TSC2. TSC1 produces the protein hamartin. TSC2 produces the protein tuberin. This disorder presents with many benign hamartomatous tumors including angiofibromas, renal angiomyolipomas, and pulmonary lymphangiomyomatosis. Tuberin and hamartin inhibit the [[Biology:MTOR|mTOR]] protein in normal cellular physiology. Inactivation of the TSC tumor suppressors causes an increase in mTOR activity. This leads to the activation of genes and the production of proteins that increase cell growth.<ref name="pmid1562401922">{{cite journal |vauthors=Inoki K, Corradetti MN, Guan KL |date=January 2005 |title=Dysregulation of the TSC-mTOR pathway in human disease |journal=Nature Genetics |volume=37 |issue=1 |pages=19–24 |doi=10.1038/ng1494 |pmid=15624019 |s2cid=205344131}}</ref><ref name="pmid170059522">{{cite journal |vauthors=Crino PB, Nathanson KL, Henske EP |date=September 2006 |title=The tuberous sclerosis complex |journal=The New England Journal of Medicine |volume=355 |issue=13 |pages=1345–1356 |doi=10.1056/NEJMra055323 |pmid=17005952 |s2cid=3579356}}</ref><ref name="pmid125562392">{{cite journal |vauthors=Kwiatkowski DJ |date=January 2003 |title=Tuberous sclerosis: from tubers to mTOR |journal=Annals of Human Genetics |volume=67 |issue=Pt 1 |pages=87–96 |doi=10.1046/j.1469-1809.2003.00012.x |pmid=12556239 |s2cid=41992893}}</ref>

===Von Hippel–Lindau disease===
[[Medicine:Von Hippel–Lindau disease|Von Hippel–Lindau disease]] is a dominantly inherited cancer syndrome that significantly increases the risk of various tumors. This includes benign hemangioblastomas and malignant [[Medicine:Pheochromocytoma|pheochromocytoma]]s, renal cell carcinomas, pancreatic endocrine tumors, and endolymphatic sac tumors. It is caused by genetic mutations in the [[Biology:Von Hippel–Lindau tumor suppressor|Von Hippel–Lindau tumor suppressor]] gene. The VHL protein (pVHL) is involved in cellular signaling in oxygen starved ([[Chemistry:Tumor hypoxia|hypoxic]]) cells. One role of pVHL is to cause the cellular degradation of another protein, [[Biology:HIF1A|HIF1α]]. Dysfunctional pVHL leads to accumulation of HIF1α. This activates several genes responsible for the production of substances involved in cell growth and blood vessel production: VEGF, [[Biology:PDGFB|PDGFβ]], TGFα and [[Biology:Erythropoietin|erythropoietin]].<ref name="pmid155790302">{{cite journal |vauthors=Maher ER |date=December 2004 |title=Von Hippel–Lindau disease |journal=Current Molecular Medicine |volume=4 |issue=8 |pages=833–842 |doi=10.2174/1566524043359827 |pmid=15579030}}</ref>

=== Bone tumors ===
Benign tumors of bone can be similar macroscopically and require a combination of a clinical history with [[Biology:Cytogenetics|cytogenetic]], molecular, and radiologic tests for diagnosis.<ref name="Garcia_2011">{{cite journal | vauthors = Garcia RA, Inwards CY, Unni KK | title = Benign bone tumors--recent developments | journal = Seminars in Diagnostic Pathology | volume = 28 | issue = 1 | pages = 73–85 | date = February 2011 | pmid = 21675379 | doi = 10.1053/j.semdp.2011.02.013 | series = Orthopaedic Pathology }}</ref> Three common forms of benign bone tumors with are giant cell tumor of bone, osteochondroma, and enchondroma; other forms of benign bone tumors exist but may be less prevalent.

==== Giant cell tumors ====
Giant cell tumors of bone frequently occur in long bone epiphyses of the [[Biology:Appendicular skeleton|appendicular skeleton]] or the [[Biology:Sacrum|sacrum]] of the [[Biology:Axial skeleton|axial skeleton]]. Local growth can cause destruction of neighboring cortical bone and soft tissue, leading to pain and limiting range of motion. The characteristic radiologic finding of giant cell tumors of bone is a lytic lesion that does not have marginal [[Medicine:Sclerosis|sclerosis]] of bone. On histology, giant cells of fused osteoclasts are seen as a response to neoplastic mononucleated cells. Notably, giant cells are not unique among benign bone tumors to giant cell tumors of bone. Molecular characteristics of the neoplastic cells causing giant cell tumors of bone indicate an origin of pluripotent mesenchymal stem cells that adopt preosteoblastic markers. Cytogenetic causes of giant cell tumors of bone involve [[Biology:Telomere|telomere]]s. Treatment involves surgical curettage with adjuvant [[Chemistry:Bisphosphonate|bisphosphonate]]s.

==== Osteochondroma ====
Osteochondromas form cartilage-capped projections of bone. Structures such as the marrow cavity and cortical bone of the osteochondroma are contiguous to those of the originating bone. Sites of origin often involve [[Biology:Metaphysis|metaphyses]] of long bones. While many osteochondromas occur spontaneously, there are cases in which several osteochondromas can occur in the same individual; these may be linked to a genetic condition known as hereditary multiple osteochondromas. Osteochondroma appears on X-ray as a projecting mass that often points away from joints.<ref name="Garcia_2011" /> These tumors stop growing with the closure of the parental bone's growth plates. Failure to stop growth can be indicative of transformation to malignant chondrosarcoma. Treatment is not indicated unless symptomatic. In that case, surgical excision is often curative.

==== Enchondroma ====
Enchondromas are benign tumors of hyaline cartilage. Within a bone, enchondromas are often found in metaphyses. They can be found in many types of bone, including small bones, long bones, and the axial skeleton. X-ray of enchondromas shows well-defined borders and a stippled appearance.<ref name="Garcia_2011" /> Presentation of multiple enchondromas is consistent with multiple enchondromatosis ([[Medicine:Ollier disease|Ollier Disease]]). Treatment of enchondromas involves surgical curettage and grafting.

=== Benign soft tissue tumors ===

==== Lipomas ====
Lipomas are benign, subcutaneous tumors of fat cells ([[Biology:Adipocyte|adipocyte]]s). They are usually painless, slow-growing, and mobile masses that can occur anywhere in the body where there are fat cells, but are typically found on the trunk and upper extremities.<ref name=":1">{{Cite journal |last1=Lichon |first1=Sabrina |last2=Khachemoune |first2=Amor |date=September 2018 |title=Clinical presentation, diagnostic approach, and treatment of hand lipomas: a review |url=https://pubmed.ncbi.nlm.nih.gov/30244263/ |journal=Acta Dermatovenerologica Alpina, Pannonica, et Adriatica |volume=27 |issue=3 |pages=137–139 |issn=1581-2979 |pmid=30244263}}</ref>

<ref name=":2">{{Citation |last1=Kolb |first1=Logan |title=Lipoma |date=2022 |url=http://www.ncbi.nlm.nih.gov/books/NBK507906/ |work=StatPearls |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=29939683 |access-date=2022-09-19 |last2=Yarrarapu |first2=Siva Naga S. |last3=Ameer |first3=Muhammad Atif |last4=Rosario-Collazo |first4=Juan A.}}</ref> Although lipomas can develop at any age, they more commonly appear between the ages of 40 and 60.<ref name=":1" /> Lipomas affect about 1% of the population, with no documented sex bias, and about 1 in every 1000 people will have a lipoma within their lifetime.<ref name=":2" /><ref>{{Citation |last1=Charifa |first1=Ahmad |title=Lipoma Pathology |date=2022 |url=http://www.ncbi.nlm.nih.gov/books/NBK482343/ |work=StatPearls |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=29493968 |access-date=2022-09-19 |last2=Azmat |first2=Chaudhary Ehtsham |last3=Badri |first3=Talel}}</ref> The cause of lipomas is not well defined. Genetic or inherited causes of lipomas play a role in around 2-3% of patients.<ref name=":2" /> In individuals with inherited familial syndromes such as [[Medicine:Proteus syndrome|Proteus syndrome]] or Familial multiple lipomatosis, it is common to see multiple lipomas across the body.<ref name=":2" /> These syndromes are also associated with specific symptoms and sub-populations. Mutations in [[Biology:Chromosome 12|chromosome 12]] have been identified in around 65% of lipoma cases.<ref name=":2" /> Lipomas have also been shown to be increased in those with obesity, hyperlipidemia, and [[Medicine:Diabetes|diabetes mellitus]].<ref name=":2" />

Lipomas are usually diagnosed clinically, although imaging ([[Physics:Ultrasound|ultrasound]], [[CT scan|computed tomography]], or [[Physics:Magnetic resonance imaging|magnetic resonance imaging]]) may be utilized to assist with the diagnosis of lipomas in atypical locations.<ref name=":1" /> The main treatment for lipomas is surgical excision, after which the tumor is examined with [[Medicine:Histopathology|histopathology]] to confirm the diagnosis.<ref name=":1" /> The prognosis for benign lipomas is excellent and recurrence after excision is rare, but may occur if the removal was incomplete.<ref name=":2" />

==Mechanism==
[[File:Types of tumor cells.jpg|thumb|Benign (L) vs Malignant tumor (R).]]

===Benign vs malignant===
[[File:BENIGN AND MALIGNANT TUMOUR.png|thumb|Diagram showing two [[Biology:Epithelium|epithelial]] tumors. The upper tumor is a benign tumor that is non-invasive. Benign tumors are usually round in shape and encapsulated by fibrous connective tissue. The lower picture depicts a malignant tumor. It is irregularly shaped, vascular, and it is invasive, crossing the basement membrane.]]
One of the most important factors in classifying a tumor as benign or malignant is its invasive potential. If a tumor lacks the ability to invade adjacent [[Biology:Tissue|tissues]] or spread to distant sites by metastasizing then it is benign, whereas invasive or metastatic tumors are malignant.<ref name="ISBN 0-443-10101-9"/> For this reason, benign tumors are not classed as cancer.<ref name="ISBN 0-7613-2833-5">{{cite book |url=https://archive.org/details/cancer00silv/page/11 |title=Cancer |vauthors=Nunn LS, Silverstein A, Silverstein VB |publisher=Twenty-First Century Books |year=2006 |isbn=0-7613-2833-5 |location=Brookfield, Conn |pages=[https://archive.org/details/cancer00silv/page/11 11–12] |url-access=registration}}</ref> Benign tumors will grow in a contained area usually encapsulated in a fibrous connective tissue capsule. The growth rates of benign and malignant tumors also differ; benign tumors generally grow more slowly than malignant tumors. Although benign tumors pose a lower health risk than malignant tumors, they both can be life-threatening in certain situations. There are many general characteristics which apply to either benign or malignant tumors, but sometimes one type may show characteristics of the other. For example, benign tumors are mostly well differentiated and malignant tumors are often undifferentiated. However, undifferentiated benign tumors and differentiated malignant tumors can occur.<ref name="pmid10366409">{{cite journal | vauthors = Skorić T, Korsić M, Zarković K, Plavsić V, Besenski N, Breskovac L, Giljević Z, Paladino J | display-authors = 6 | title = Clinical and morphological features of undifferentiated monomorphous GH/TSH-secreting pituitary adenoma | journal = European Journal of Endocrinology | volume = 140 | issue = 6 | pages = 528–537 | date = June 1999 | pmid = 10366409 | doi = 10.1530/eje.0.1400528 | doi-access = free }}</ref><ref name="pmid23106056">{{cite journal | vauthors = Song HJ, Xue YL, Qiu ZL, Luo QY | title = Uncommon metastases from differentiated thyroid carcinoma | journal = Hellenic Journal of Nuclear Medicine | volume = 15 | issue = 3 | pages = 233–240 | year = 2012 | pmid = 23106056 | doi = <!-- 10.1967/s002449910059 --> }}</ref> Although benign tumors generally grow slowly, cases of fast-growing benign tumors have also been documented.<ref name="pmid5681331">{{cite journal | vauthors = Sagel SS, Ablow RC | title = Hamartoma: on occasion a rapidly growing tumor of the lung | journal = Radiology | volume = 91 | issue = 5 | pages = 971–972 | date = November 1968 | pmid = 5681331 | doi = 10.1148/91.5.971 }}</ref> Some malignant tumors are mostly non-metastatic such as in the case of [[Medicine:Basal-cell carcinoma|basal-cell carcinoma]].<ref name="ISBN 0-7817-9516-8">{{cite book |title=Rubin's pathology: clinicopathologic foundations of medicine |vauthors=Strayer DL, Rubin R, Rubin E |publisher=Wolters Kluwer/Lippincott Williams & Wilkins |year=2008 |isbn=978-1605479682 |location=Philadelphia |pages=138–139}}</ref> CT and chest radiography can be a useful diagnostic exam in visualizing a benign tumor and differentiating it from a malignant tumor. The smaller the tumor on a radiograph the more likely it is to be benign as 80% of lung nodules less than 2&nbsp;cm in diameter are benign. Most benign nodules are smoothed radiopaque densities with clear margins but these are not exclusive signs of benign tumors.<ref>{{cite journal | vauthors = Erasmus JJ, Connolly JE, McAdams HP, Roggli VL | title = Solitary pulmonary nodules: Part I. Morphologic evaluation for differentiation of benign and malignant lesions | journal = Radiographics | volume = 20 | issue = 1 | pages = 43–58 | date = 2000 | pmid = 10682770 | doi = 10.1148/radiographics.20.1.g00ja0343 }}</ref>

===Multistage carcinogenesis===
Tumors are formed by [[Biology:Carcinogenesis|carcinogenesis]], a process in which cellular alterations lead to the formation of cancer. Multistage carcinogenesis involves the sequential [[Biology:Genetics|genetic]] or epigenetic changes to a cell's [[Biology:DNA|DNA]], where each step produces a more advanced tumor. It is often broken down into three stages; initiation, promotion and progression, and several mutations may occur at each stage. Initiation is where the first genetic mutation occurs in a cell. Promotion is the clonal expansion (repeated division) of this transformed cell into a visible tumor that is usually benign. Following promotion, progression may take place where more genetic mutations are acquired in a sub-population of tumor cells. Progression changes the benign tumor into a malignant tumor.<ref name="pmid1911211">{{cite journal |vauthors=Clark WH |date=October 1991 |title=Tumour progression and the nature of cancer |journal=British Journal of Cancer |volume=64 |issue=4 |pages=631–644 |doi=10.1038/bjc.1991.375 |pmc=1977704 |pmid=1911211}}</ref><ref name="pmid8354184">{{cite journal | vauthors = Barrett JC | title = Mechanisms of multistep carcinogenesis and carcinogen risk assessment | journal = Environmental Health Perspectives | volume = 100 | pages = 9–20 | date = April 1993 | pmid = 8354184 | pmc = 1519586 | doi = 10.1289/ehp.931009 }}</ref> A prominent and well studied example of this phenomenon is the tubular adenoma, a common type of colon polyp which is an important precursor to colon cancer. The cells in tubular adenomas, like most tumors that frequently progress to cancer, show certain abnormalities of cell maturation and appearance collectively known as [[Biology:Dysplasia|dysplasia]]. These cellular abnormalities are not seen in benign tumors that rarely or never turn cancerous, but are seen in other pre-cancerous tissue abnormalities which do not form discrete masses, such as pre-cancerous lesions of the uterine cervix.

==Diagnosis==
===Classification===
{| class="wikitable mw-collapsible floatright"
|+ Tumors and cell origin
! Cell origin
! Cell type
! Tumor
 |-
! rowspan ="10" | Endodermal
| Biliary tree|| Cholangioma
|-
 | Colon || Colonic polyp
|-
 |rowspan="3"| Glandular || [[Medicine:Adenoma|Adenoma]]
|-
|[[Medicine:Papilloma|Papilloma]]
|-
| Cystadenoma
|-
 | [[Biology:Liver|Liver]] || [[Medicine:Hepatocellular adenoma|Liver cell adenoma]]
|-
 | [[Biology:Placenta|Placenta]]l || Hydatiform mole
|-
 | Renal || Renal tubular adenoma
|-
 | Squamous || Squamous cell papilloma
|-
 | [[Biology:Stomach|Stomach]] || Gastric polyp
|-
! rowspan ="8" | Mesenchymal
| [[Biology:Blood vessel|Blood vessel]] || Hemangioma, Cardiac myxoma
|-
|[[Biology:Bone|Bone]]||Osteoma
|-
|[[Biology:Cartilage|Cartilage]]||Chondroma
|-
|Fat tissue||[[Medicine:Lipoma|Lipoma]]
|-
|Fibrous tissue||Fibroma
|-
|Lymphatic vessel||Lymphangioma
|-
|[[Biology:Smooth muscle|Smooth muscle]]||[[Medicine:Leiomyoma|Leiomyoma]]
|-
|Striated muscle||[[Medicine:Rhabdomyoma|Rhabdomyoma]]
|-
! rowspan = "4" | Ectodermal
| Glia || Astrocytoma, Schwannoma
|-
|[[Biology:Melanocyte|Melanocyte]]s||Nevus
|-
|[[Medicine:Meninges|Meninges]]||[[Medicine:Meningioma|Meningioma]]
|-
|Nerve cells||Ganglioneuroma
|-
!colspan="3"|Reference<ref name="ISBN 0-7637-6357-8">{{cite book | vauthors = Wujcik D, Yarbro CH, Gobel BH |title=Cancer nursing: principles and practice |publisher=Jones and Bartlett Publishers |location=Boston|year=2011 |isbn=978-0-7637-6357-2 }}</ref>
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Benign [[Medicine:Neoplasm|neoplasm]]s are typically, but not always, composed of cells which bear a strong resemblance to a normal cell type in their organ of origin. These tumors are named for the cell or tissue type from which they originate. The suffix "-oma" (but not -carcinoma, -sarcoma, or -blastoma, which are generally cancers) is applied to indicate a benign tumor. For example, a [[Medicine:Lipoma|lipoma]] is a common benign tumor of fat cells (lipocytes), and a chondroma is a benign tumor of cartilage-forming cells ([[Biology:Chondrocyte|chondrocyte]]s). [[Medicine:Adenoma|Adenoma]]s are benign tumors of gland-forming cells, and are usually specified further by their cell or organ of origin, as in hepatic adenoma (a benign tumor of [[Biology:Hepatocyte|hepatocyte]]s, or [[Biology:Liver|liver]] cells). [[Medicine:Teratoma|Teratoma]]s contain many cell types such as skin, nerve, brain and thyroid, among others, because they are derived from germ cells.<ref name="ISBN 0-7817-9516-82">{{cite book |title=Rubin's pathology: clinicopathologic foundations of medicine |vauthors=Strayer DL, Rubin R, Rubin E |publisher=Wolters Kluwer/Lippincott Williams & Wilkins |year=2008 |isbn=978-0-7817-9516-6 |location=Philadelphia |pages=138–139}}</ref> [[Medicine:Hamartoma|Hamartoma]]s are a group of benign tumors that have relatively normal [[Biology:Cellular differentiation|cellular differentiation]] but exhibit disorganized tissue organization.<ref name="pmid1562401922"/>

Exceptions to the nomenclature rules exist for historical reasons; malignant examples include [[Medicine:Melanoma|melanoma]] (a cancer of pigmented skin cells, or melanocytes) and seminoma (a cancer of male reproductive cells).<ref name="robbins2">{{cite book |title=Robbins Pathologic Basis of Disease |vauthors=Cotran R, Kumar V, Collins T |publisher=W.B. Saunders |year=1999 |isbn=0-7216-7335-X |edition=6th}}</ref>

Benign tumors do not encompass all benign growths. Skin tags, vocal chord polyps, and hyperplastic polyps of the colon are often referred to as benign, but they are [[Medicine:Hyperplasia|overgrowths of normal tissue]] rather than neoplasms.<ref name="ISBN 0-7817-9516-82" />

==Treatment==
Benign tumors typically need no treatment unless if they cause problems such as seizures, discomfort or cosmetic concerns. [[Medicine:Surgery|Surgery]] is usually the most effective approach and is used to treat most benign tumors. In some cases, other treatments may be used. Adenomas of the [[Biology:Rectum|rectum]] may be treated with [[Medicine:Sclerotherapy|sclerotherapy]], in which chemicals are used to shrink blood vessels in order to cut off the blood supply.<ref name="zuberandharder12">{{cite book |url=https://www.ncbi.nlm.nih.gov/books/NBK6994/ |title=Benign tumors of the colon and rectum |vauthors=Zuber M, Harder F |publisher=Surgical Treatment: Evidence-Based and Problem-Oriented. |year=2001 |location=Munich: Zuckschwerdt}}</ref> Most benign tumors do not respond to [[Medicine:Chemotherapy|chemotherapy]] or [[Physics:Radiation therapy|radiation therapy]], although there are exceptions; benign intercranial tumors are sometimes treated with radiation therapy and chemotherapy under certain circumstances.<ref name="pmid234627042">{{cite journal |vauthors=Brada M |date=February 2013 |title=Radiotherapy for benign brain tumours coming of age; example of vestibular schwannoma |journal=Radiotherapy and Oncology |volume=106 |issue=2 |pages=157–160 |doi=10.1016/j.radonc.2013.01.009 |pmid=23462704}}</ref><ref name="pmid190235202">{{cite journal |vauthors=Sioka C, Kyritsis AP |date=March 2009 |title=Chemotherapy, hormonal therapy, and immunotherapy for recurrent meningiomas |journal=Journal of Neuro-Oncology |volume=92 |issue=1 |pages=1–6 |doi=10.1007/s11060-008-9734-y |pmid=19023520 |s2cid=28106960}}</ref> Radiation can also be used to treat hemangiomas in the rectum.<ref name="zuberandharder12" /> Benign skin tumors are usually surgically resected but other treatments such as [[Unsolved:Cryotherapy|cryotherapy]], [[Medicine:Curettage|curettage]], electrodesiccation, laser therapy, [[Medicine:Dermabrasion|dermabrasion]], chemical peels and [[Medicine:Topical medication|topical medication]] are used.<ref name="pmid126137272">{{cite journal |vauthors=Luba MC, Bangs SA, Mohler AM, Stulberg DL |date=February 2003 |title=Common benign skin tumors |journal=American Family Physician |volume=67 |issue=4 |pages=729–738 |pmid=12613727}}</ref><ref name="pmid183956712">{{cite journal |vauthors=Marghoob AA, Borrego JP, Halpern AC |date=December 2007 |title=Congenital melanocytic nevi: treatment modalities and management options |journal=Seminars in Cutaneous Medicine and Surgery |volume=26 |issue=4 |pages=231–240 |doi=10.1016/j.sder.2008.03.007 |pmid=18395671}}</ref>


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[[Category:Medical terminology]]

{{Sourceattribution|Benign tumor}}