View source for Lipoma

{{short description|Benign tumor made of fat tissue}}
{{cs1 config|name-list-style=vanc}}
{{Infobox medical condition (new)
| name            = Lipoma
| image           = Lipoma 02.jpg
| caption         = Lipoma on [[forearm]]
|image2          = Small_lipomas_removed_from_arms.jpg
|caption2        = Small lipomas which have been removed
| field           = [[Dermatology]], [[general surgery]], [[oncology]]
| symptoms        = Soft, movable, usually painless lump<ref name=AO2012 />
| complications   =
| onset           = 40 to 60 years old<ref name=AO2012 />
| duration        =
| types           = Superficial, deep<ref name=Kr2006 />
| causes          = Unclear<ref name=AO2012 />
| risks           = Family history, [[obesity]], insufficient exercise<ref name=AO2012 /><ref name=Fle2002 />
| diagnosis       = Based on [[physical exam]]<ref name=AO2012 />
| differential    = [[Liposarcoma]], [[hibernoma]], [[lipomatosis]], [[ganglion cyst]]<ref name=Lin2015 />
| prevention      =
| treatment       = [[watchful waiting|Observation]], surgery<ref name=AO2012 />
| medication      =
| prognosis       = Good<ref name=AO2012 />
| frequency       = ~2%<ref name=Kr2006 />
| deaths          =
}}
<!-- Definition and symptoms -->
A '''lipoma''' is a [[benign tumor]] made of [[adipose tissue|fat tissue]].<ref name=AO2012>{{cite web|title=Lipoma-OrthoInfo – AAOS|url=http://orthoinfo.aaos.org/topic.cfm?topic=a00631|website=orthoinfo.aaos.org|access-date=8 November 2017|date=May 2012}}</ref> They are generally soft to the touch, movable, and painless.<ref name=AO2012 /> They usually occur just under the skin, but occasionally may be deeper.<ref name=AO2012 /> Most are less than {{cvt|5|cm}} in size.<ref name=Kr2006>{{cite book|last1=Kransdorf|first1=Mark J.|last2=Murphey|first2=Mark D.|title=Imaging of Soft Tissue Tumors|date=2006|publisher=Lippincott Williams & Wilkins|isbn=978-0-7817-4771-4|page=81|url=https://books.google.com/books?id=0ZA6ntBA76MC&pg=PA81|language=en}}</ref> Common locations include upper back, shoulders, and [[abdomen]].<ref name=Lin2015>{{cite book|last1=Lindberg|first1=Matthew R.|title=Diagnostic Pathology: Soft Tissue Tumors E-Book|date=2015|publisher=Elsevier Health Sciences|isbn=978-0-323-40041-1|page=44|url=https://books.google.com/books?id=aSZACgAAQBAJ&q=Lipoma%20%22differential%20diagnosis%22&pg=PA44|language=en}}</ref> It is possible to have several lipomas.<ref name=Fle2002 />

<!-- Cause and diagnosis -->
The cause is generally unclear.<ref name=AO2012 /> Risk factors include family history, [[obesity]], and lack of exercise.<ref name=AO2012 /><ref name=Fle2002>{{cite book|last1=Fletcher|first1=Christopher D. M.|last2=Unni|first2=K. Krishnan|last3=Mertens|first3=Fredrik|title=Pathology and Genetics of Tumours of Soft Tissue and Bone|date=2002|publisher=IARC|isbn=978-92-832-2413-6|page=20|url=https://books.google.com/books?id=dg9am0g4EP8C&pg=PA20|language=en}}</ref> Diagnosis is typically based on a [[physical exam]].<ref name=AO2012 /> Occasionally [[medical imaging]] or [[tissue biopsy]] is used to confirm the diagnosis.<ref name=AO2012 />

<!-- Treatment and prognosis -->
Treatment is typically by [[watchful waiting|observation]] or surgical removal.<ref name=AO2012 /> Rarely, the condition may recur following removal, but this can generally be managed with repeat surgery.<ref name=AO2012 /> Lipomas are not generally associated with a future risk of [[cancer]].<ref name=AO2012 />

<!-- Epidemiology and history -->
Lipomas have a prevalence of roughly 2 out of every 100 people.<ref name=Kr2006 /> Lipomas typically occur in adults between 40 and 60 years of age.<ref name=AO2012 /> Males are more often affected than females.<ref name=AO2012 /> They are the most common noncancerous [[soft tissue|soft-tissue]] tumor.<ref>{{cite journal |vauthors=Bancroft LW, Kransdorf MJ, Peterson JJ, O'Connor MI |title=Benign fatty tumors: classification, clinical course, imaging appearance, and treatment |journal=Skeletal Radiol. |volume=35 |issue=10 |pages=719–33 |date=October 2006 |pmid=16927086 |doi=10.1007/s00256-006-0189-y|s2cid=6388113 }}</ref> The first use of the term "lipoma" to describe these tumors was in 1709.<ref>{{cite book|last1=Olson|first1=James Stuart|title=The History of Cancer: An Annotated Bibliography|date=1989|publisher=ABC-CLIO|isbn=978-0-313-25889-3|page=15|url=https://books.google.com/books?id=oAX8jOJ9uO0C&pg=PA15|language=en}}</ref>

==Etymology==
"Fatty tumor" (plural ''lipomata''), 1830, medical Latin, from Greek ''lipos'' "fat" (n.), from [[Proto-Indo-European language|PIE]] root ''*leip-'' "to stick, adhere", also used to form words for "fat", + ''-oma''.

== Types ==
The many subtypes of lipomas include:<ref name="Andrews">{{cite book| edition = 10th| publisher = Elsevier| isbn = 978-0-7216-2921-6| last1 = James| first1 = William D.| first2 = Timothy G. |last2=Berger|first3= Dirk M.|last3= Elston| title = Andrews' Diseases of the Skin: Clinical Dermatology|location=London|year=2005}}</ref>{{Rp|624–25}}
* [[Adenolipoma]]s are lipomas associated with [[eccrine sweat glands]].<ref name="Andrews new ed.">{{cite book| edition = 11th| publisher = Elsevier| isbn = 978-1-4377-0314-6| last1 = James| first1 = William D.| first2 = Timothy G. |last2=Berger|first3= Dirk M.|last3= Elston| title = Andrews' Diseases of the Skin: Clinical Dermatology|location=London|year=2011}}</ref>{{rp|627}}
* [[Angiolipoleiomyoma]]s are acquired, solitary, asymptomatic [[wikt:acral|acral]] nodules, characterized histologically by well-circumscribed subcutaneous tumors composed of smooth muscle cells, blood vessels, connective tissue, and fat.<ref name="Andrews" />{{rp|627}}
* [[Angiolipoma]]s are painful subcutaneous nodules having all other features of a typical lipoma.<ref name="Andrews" />{{rp|624}}<ref name="Bolognia">{{cite book |last1=Rapini |first1=Ronald P. |last2=Bolognia |first2=Jean L. |last3=Jorizzo |first3=Joseph L. |title=Dermatology: 2-Volume Set |publisher=Mosby |location=St. Louis |year=2007 |isbn=978-1-4160-2999-1 }}</ref>
* [[Cerebellar pontine angle]] and [[internal auditory canal]] lipomas<ref>{{cite journal |vauthors=Crowson MG, Symons SP, Chen JM | year = 2013| title = Left cerebellopontine angle lipoma with mild brainstem compression in a 13-year-old female | journal = Otology & Neurotology | volume = 34| issue = 5| pages = e34–e35| doi=10.1097/mao.0b013e3182814d6e| pmid = 23507992}}</ref>
* [[Chondroid lipoma]]s are deep-seated, firm, yellow tumors that characteristically occur on the legs of women.<ref name="Andrews" />{{rp|625}}
* [[Corpus callosum]] lipoma is a rare congenital brain condition that may or may not present with symptoms.<ref>{{cite journal |last=Wallace |first=D. |title=Lipoma of the corpus callosum |journal=Journal of Neurology, Neurosurgery, and Psychiatry |volume=39 |issue=12 |pages=1179–1185 |date=December 1976 |pmid=1011028 |pmc=492562 |doi= 10.1136/jnnp.39.12.1179}}</ref> This occurs in the corpus callosum, also known as the calossal [[commissure]], which is a wide, flat bundle of neural fibers beneath the cortex in the human brain.
* [[Hibernoma]]s are lipomas of [[brown fat]].
* [[Intradermal spindle cell lipoma]]s are distinct in that they most commonly affect women and have a wide distribution, occurring with relatively equal frequency on the head and neck, trunk, and upper and lower extremities.<ref name="Andrews" />{{rp|625}}<ref name="Bolognia" />[[File:Histopathology of a fibrolipoma.jpg|thumb|Fibrolipoma: Large amounts of fibrous tissue]]
* A ''fibrolipoma'' is a lipoma with focal areas of large amounts of fibrous tissue. A ''sclerotic lipoma'' is a predominantly fibrous lesion with focal areas of fat.<ref>{{cite web|url=http://surgpathcriteria.stanford.edu/softfat/lipoma/fibrolipoma.html|title=Lipoma Variant: Fibrolipoma|website=[[Stanford University School of Medicine]]|access-date=2020-02-10|archive-date=2020-02-12|archive-url=https://web.archive.org/web/20200212033936/http://surgpathcriteria.stanford.edu/softfat/lipoma/fibrolipoma.html|url-status=dead}}</ref>
** [[Neural fibrolipoma]]s are overgrowths of fibro-fatty tissue along a nerve trunk, which often leads to nerve compression.<ref name="Andrews" />{{rp|625}}
* [[Pleomorphic lipoma]]s, like spindle-cell lipomas, occur for the most part on the backs and necks of elderly men and are characterized by floret giant cells with overlapping nuclei.<ref name="Andrews" />{{rp|625}}
* [[Spindle-cell lipoma]]s are asymptomatic, slow-growing, subcutaneous tumors that have a predilection for the posterior back, neck, and shoulders of older men.<ref name="Andrews" />{{rp|625}}
* Superficial subcutaneous lipomas, the most common type of lipoma, lie just below the surface of the skin.<ref name=emedicine2720>{{EMedicine|med|2720|Lipomas}}</ref> Most occur on the [[torso|trunk]], [[thigh]], and [[forearm]], although they may be found anywhere in the body where fat is located.<ref>{{cite web |url=https://www.lecturio.com/concepts/lipoma/ | title=Lipoma |website=The Lecturio Medical Concept Library |access-date= 6 August 2021}}</ref>

== Causes ==
The tendency to develop a lipoma is not necessarily hereditary, although hereditary conditions such as [[lipomatosis|familial multiple lipomatosis]] might include lipoma development.<ref>{{cite journal |vauthors=Leffell DJ, Braverman IM |title=Familial multiple lipomatosis. Report of a case and a review of the literature |journal=J. Am. Acad. Dermatol. |volume=15 |issue=2 Pt 1 |pages=275–9 |date=August 1986 |pmid=3745530 |doi=10.1016/S0190-9622(86)70166-7}}</ref><ref>{{cite journal |author=Toy BR |title=Familial multiple lipomatosis |journal=Dermatol. Online J. |volume=9 |issue=4 |pages=9 |date=October 2003 |doi=10.5070/D37088D8PK |pmid=14594582 |url=http://dermatology.cdlib.org/94/NYU/Jan2002/2.html|url-access=subscription }}</ref> Genetic studies in mice have shown a correlation between the ''HMG I-C'' gene (previously identified as a gene related to obesity) and lipoma development. These studies support prior epidemiologic data in humans showing a correlation between ''HMG I-C'' and [[mesenchymal tumour|mesenchymal tumors]].<ref>{{cite journal |vauthors=Arlotta P, Tai AK, Manfioletti G, Clifford C, Jay G, Ono SJ |title= Transgenic mice expressing a truncated form of the high mobility group I-C protein develop adiposity and an abnormally high prevalence of lipomas |journal=J Biol Chem|volume=275|issue=19 |pages=14394–400|date=May 2000 |pmid=10747931 | doi=10.1074/jbc.M000564200|doi-access=free }}</ref>

Cases have been reported where minor injuries are alleged to have triggered the growth of a lipoma, called a "post-traumatic lipoma".<ref>{{cite journal |vauthors=Signorini M, Campiglio GL |title=Posttraumatic lipomas: where do they really come from? |journal=Plast. Reconstr. Surg. |volume=101 |issue=3 |pages=699–705 |date=March 1998 |pmid=9500386 |doi=10.1097/00006534-199803000-00017|s2cid=44745524 }}</ref> However, the link between trauma and the development of lipomas is controversial.<ref>{{cite journal |vauthors=Aust MC, Spies M, Kall S, Jokuszies A, Gohritz A, Vogt P |title=Posttraumatic lipoma: fact or fiction? |journal=Skinmed |volume=6 |issue=6 |pages=266–70 |year=2007 |pmid=17975353 |url=http://www.lejacq.com/articleDetail.cfm?pid=SKINmed_6;6:266 |archive-url=https://archive.today/20090215143117/http://www.lejacq.com/articleDetail.cfm?pid=SKINmed_6;6:266 |url-status=dead |archive-date=2009-02-15 |doi=10.1111/j.1540-9740.2007.06361.x |url-access=subscription }}</ref>

=== Other conditions ===
[[Lipomatosis]] is believed to be a hereditary condition in which multiple lipomas are present on the body.{{citation needed|date=September 2021}}

[[Adiposis dolorosa]] (Dercum disease) is a rare condition involving multiple painful lipomas, swelling, and fatigue. Early studies mentioned prevalence in obese postmenopausal women.  However, current{{when?|date=July 2025}} literature demonstrates that Dercum disease is present in more women than men of all body types; the average age for diagnosis is 35 years.<ref>{{Cite web |url=http://www.lipomadoc.org/uploads/5/0/4/8/5048532/dd_white_paper.pdf |title=Dercum's Disease White Paper |first=Karen Louise |last=Herbst |year=2012 |archive-url=https://web.archive.org/web/20241203042115/http://www.lipomadoc.org/uploads/5/0/4/8/5048532/dd_white_paper.pdf |archive-date=2024-12-03}}</ref>{{self-published source|date=July 2025}}

[[Benign symmetric lipomatosis]] (Madelung disease) is another condition involving lipomatosis. It nearly always appears in middle-aged males after many years of [[alcoholism]], but nonalcoholic males and females can also be affected.<ref>{{cite book |author=Rapini, Ronald P. |author2=Bolognia, Jean L. |author3=Jorizzo, Joseph L. |title=Dermatology: 2-Volume Set |publisher=Mosby |location=St. Louis |year=2007 |isbn=978-1-4160-2999-1 }}</ref>

== Diagnosis ==
A physical exam is typically the easiest way to diagnose it. Rarely, a tissue biopsy or imaging may be required. The imaging modality of choice is [[magnetic resonance imaging]] (MRI) because it has superior sensitivity of distinguishing it from [[liposarcoma]] as well as mapping the surrounding anatomy.<ref>{{cite web|url=https://radiopaedia.org/articles/lipoma|title=Lipoma|author=Rohit Sharma |author2=Frank Gaillard |display-authors=etal|access-date=2018-09-27|website=Radiopaedia}}</ref>

<gallery mode="packed">
File:Lipoma 05.jpg|X-ray of a lipoma
File:Ultrasonography of a lipoma.jpg|[[Medical ultrasonography]] of a lipoma in the [[thenar eminence]]: It is hyperechoic compared to adjacent muscle, and relatively well-defined, with miniature hyperechoic lines.<ref name=Chernev2013>{{cite journal |last1=Chernev |first1=Ivan |last2=Tingey |first2=Spencer |title=Thenar Intramuscular Lipoma: A Case Report |journal=Journal of Medical Cases |volume=4 |issue=10 |pages=676–678 |date=2013 |doi=10.4021/jmc1474w |citeseerx=10.1.1.868.8123 }}</ref>
File:T1 MRI of thenar intramuscular lipoma.jpg|alt=T1 MRI of the same lipoma: High intensity signal mass with regions of ill-defined margins.|[[Magnetic resonance imaging#T1 and T2|T1 MRI]] of the same lipoma: High intensity signal mass with regions of ill-defined margins<ref name=Chernev2013 />
File:Scrotal ultrasonography of liposarcoma.jpg|Ultrasonography of a [[liposarcoma]] for comparison: In this case a heterogeneous mass consisting of an upper hyperechoic portion, corresponding to lipomatous matrix, and areas of hypoechogenicity corresponding to nonlipomatous components.<ref name="MakTzeng2012">Content originally copied from: {{cite book|last1=Mak|first1=Chee-Wai|last2=Tzeng|first2=Wen-Sheng|chapter=Sonography of the Scrotum|chapter-url=https://www.intechopen.com/books/sonography/sonography-of-the-scrotum |editor=Kerry Thoirs |title=Sonography |year=2012|doi=10.5772/27586|isbn=978-953-307-947-9}} Published under the [https://creativecommons.org/licenses/by/3.0/ CC-BY-3.0 license].</ref><!-- This is content from a predatory publisher (intechopen.com); recommend finding an alternative source for a comparable image, but I hesitate to remove the image at this time. -->
File:Scrotal ultrasonography of liposarcoma mimicking a lipoma.jpg|Ultrasonography of a [[liposarcoma]] mimicking lipoma. A homogeneous hypoechoic mass presenting with the same appearance of lipoma. It was clinically distinguished by having rapid growth.<ref name="MakTzeng2012" />
File:Arm mri.jpg|MRI showing lipoma of the arm
File:Medical X-Ray imaging TPH07 nevit.jpg|X-ray showing lipoma
File:Lipoma illness.jpg
File:Gould Pyle 241.jpg|Large fibrolipoma
File:Gould Pyle 242.jpg|Diffuse lipomas of the neck and abdomen
File:Gould Pyle 243.jpg|Enormous lipoma of the [[parietal bone|parietal region]]
File:Histopathology of lipoma.jpg|[[Histopathology]] of a lipoma: The mass is composed of lobules of mature white adipose tissue divided by fibrous septa containing thin-walled capillary-sized vessels.<ref name="Kim2016">{{cite journal |last1=Kim |first1=Hei Sung |title=Lipoma on the antitragus of the ear |journal=Journal of Clinical Research in Dermatology |date=30 March 2016 |volume=3 |issue=2 |pages=01–02 |doi=10.15226/2378-1726/3/2/00121 }}</ref>{{predatory publisher}} H&E stain.
File:Histopathology of an atypical lipomatous tumor or well-differentiated liposarcoma, lipoma-like subtype.jpg|Histopathology of the major differential diagnosis of a well-differentiated [[liposarcoma]], lipoma-like subtype: It looks almost identical at low magnification, but a high magnification of a fibrous band shows spindle cells with enlarged, hyperchromatic nuclei. H&E stain.
File:Osseous formation in a well-differentiated liposarcoma.jpg|Bone formation may be seen in both lipomas<ref name="KuyamaFifita2009">{{cite journal|last1=Kuyama|first1=Kayo|last2=Fifita|first2=Sisilia Fusi|last3=Komiya|first3=Masamichi|last4=Sun|first4=Yan|last5=Akimoto|first5=Yoshiaki|last6=Yamamoto|first6=Hirotsugu|title=Rare Lipomatous Tumors with Osseous and/or Chondroid Differentiation in the Oral Cavity Report of Two Cases and Review of the Literature|journal=International Journal of Dentistry|volume=2009|year=2009|pages=1–6|issn=1687-8728|doi=10.1155/2009/143460|pmid=20309407|pmc=2837472|doi-access=free}}</ref> and liposarcomas (a well-differentiated one pictured).
</gallery>

== Treatment ==
Usually, treatment of lipomas is not necessary, unless they become painful or restrict movement. They are usually removed for cosmetic reasons if they grow very large or for [[histopathology]] to verify that they are not a more dangerous type of tumor such as a liposarcoma.<ref name=emedicine2720 /> This last point can be important, as the characteristics of a tumor are not known until after it is removed and medically examined.{{citation needed|date=October 2020}}

Lipomas are normally removed by simple excision.<ref name=Salam /> The removal can often be done under local anesthetic and takes less than 30 minutes. This cures the great majority of cases, with about 1–2% of lipomas recurring after excision.<ref name=Dalal>{{cite journal |vauthors=Dalal KM, Antonescu CR, Singer S |title=Diagnosis and management of lipomatous tumors |journal=J Surg Oncol |volume=97 |issue=4 |pages=298–313 |date=March 2008 |pmid=18286473 |doi=10.1002/jso.20975|s2cid=22021575 |doi-access=free }}</ref> [[Liposuction]] is another option if the lipoma is soft and has a small [[connective tissue]] component. Liposuction typically results in less [[scar]]ring; however, with large lipomas, it may fail to remove the entire tumor, which can lead to regrowth.<ref>{{cite journal |vauthors=Al-basti HA, El-Khatib HA |title=The use of suction-assisted surgical extraction of moderate and large lipomas: long-term follow-up |journal=Aesthetic Plast Surg |volume=26 |issue=2 |pages=114–7 |year=2002 |pmid=12016495 |doi=10.1007/s00266-002-1492-1|s2cid=6701609 }}</ref>

New methods under development are supposed to remove the lipomas without scarring. One is removal by injecting compounds that trigger [[lipolysis]], such as [[steroid]]s or [[phosphatidylcholine]].<ref name=Salam /><ref>{{cite journal  |vauthors=Bechara FG, Sand M, Sand D, etal |title=Lipolysis of lipomas in patients with familial multiple lipomatosis: an ultrasonography-controlled trial |journal=J Cutan Med Surg |volume=10 |issue=4 |pages=155–9 |year=2006 |pmid=17234112 |doi=10.2310/7750.2006.00040|s2cid=45970041 }}</ref> Other potential methods based on tissue-targeted heating include [[cauterization]], [[electrosurgery]], and [[harmonic scalpel]].<ref>{{cite journal |last1=Boyer |first1=M |title=A review of techniques and procedures for lipoma treatment |journal= Clinical Dermatology|date=2015 |doi=10.11138/cderm/2015.3.4.105  |doi-access=free }}</ref>

===Post surgery===
Patients who have a lipoma removed are usually able to return home the same day, without any need for hospitalization. Some patients may have pain, swelling, or bruising where the lipoma was removed. These symptoms usually subside after a few days.<ref>{{cite web |url=https://www.drugs.com/cg/lipoma-removal-ambulatory-care.html |title=Lipoma Removal |publisher=[[Drugs.com]] |accessdate=2021-03-05 }}</ref>

<gallery caption="Resection of an intermuscular lipoma in the elbow region">
File:Lipoma 03.jpg|Intraoperative photo
File:Lipoma 04.jpg|[[Operating field]] after removal of the lipoma: Arrow marks the [[median nerve]] that was compressed by the lipoma.
File:Lipoma 06.jpg|The resected lipoma<br />(8&nbsp;cm × 6&nbsp;cm × 3&nbsp;cm)
</gallery>
<gallery caption="Other lipomas">
File:Lipoma.JPG|Lipoma removed from human torso
File:Lipoma(1).JPG|Lipoma removed from the breast
File:Lipoma from thigh.jpg|This lipoma was removed from the thigh of a 39-year-old male patient. It measured about 10&nbsp;cm in diameter at the time of removal. In the center is a section of skin that was removed with the lipoma.
File:Small lipomas removed from arms.jpg|A collection of small lipomas removed from the arms of a patient
</gallery>

== Prognosis ==
Lipomas are rarely life-threatening, and the common subcutaneous lipomas are not a serious condition. Lipomas growing in internal organs can be more dangerous; for example, lipomas in the gastrointestinal tract can cause bleeding, [[Peptic ulcer|ulceration]], and painful obstructions (so-called "malignant by location", despite being a benign growth histologically).<ref>{{cite journal |author=Thompson WM |title=Imaging and findings of lipomas of the gastrointestinal tract |journal=AJR Am J Roentgenol |volume=184 |issue=4 |pages=1163–71 |date=1 April 2005|pmid=15788588 |doi=10.2214/ajr.184.4.01841163}}</ref><ref>{{cite journal |vauthors=Taylor AJ, Stewart ET, Dodds WJ |title=Gastrointestinal lipomas: a radiologic and pathologic review |journal=AJR Am J Roentgenol |volume=155 |issue=6 |pages=1205–10 |date=1 December 1990|pmid=2122666 |doi=10.2214/ajr.155.6.2122666|doi-access=free }}</ref> [[Malignancy|Malignant]] transformation of lipomas into liposarcomas is very rare, and most liposarcomas are not produced from pre-existing benign lesions.<ref name=Dalal /> A few cases of malignant transformation have been described for bone and kidney lipomas,<ref>{{cite journal |author=Milgram JW |title=Malignant transformation in bone lipomas |journal=Skeletal Radiol. |volume=19 |issue=5 |pages=347–52 |year=1990 |pmid=2165632 |doi=10.1007/BF00193088|s2cid=5897104 }}</ref><ref>{{cite journal |vauthors=Lowe BA, Brewer J, Houghton DC, Jacobson E, Pitre T |title=Malignant transformation of angiomyolipoma |journal=J. Urol. |volume=147 |issue=5 |pages=1356–8 |date=May 1992 |pmid=1569683|doi=10.1016/S0022-5347(17)37564-X }}</ref> but it is possible that these few reported cases were well-differentiated liposarcomas in which the subtle malignant characteristics were missed when the tumor was first examined.<ref name=Enzinger08>{{cite book |author1=Goldblum, John R. |author2=Weiss, Sharon W. |author3=Enzinger, Franz M. |title=Enzinger and Weiss's soft tissue tumors |publisher=Mosby Elsevier |year=2008 |isbn=978-0-323-04628-2 |edition=5th}}</ref> Deep lipomas have a greater tendency to recur than superficial lipomas because complete surgical removal of deep lipomas is not always possible.<ref name=Enzinger08 /><ref>{{cite book |editor-last1=Fletcher |editor-first1=C.D.M. |editor-last2=Unni |editor-first2=K.K. |editor-last3=Mertens |editor-first3=F. |title=Pathology and Genetics of Tumours of Soft Tissue and Bone |publisher=IARC Press |location=Lyon |year=2002 |isbn=978-92-832-2413-6 |series=World Health Organization Classification of Tumours |volume=4}}</ref>

The presence of multiple lipomas, [[lipomatosis]], is more commonly encountered in men. Some superficial lipomas can extend into deep [[fascia]] and may complicate excision. Liposarcoma is found in 1% of lipomas and is more likely to occur in lesions of the lower extremities, shoulders, and [[retroperitoneal]] areas. Other risk factors for liposarcoma include large size (>5&nbsp;cm), associated with [[calcification]], rapid growth, and/or invasion into nearby structures or through fascia into [[muscle tissue]].<ref>E.J. Mayeaux Jr. (2009). [https://books.google.com/books?id=d-wNb7eyonMC&dq=can+lipoma+penetrate+fascia&pg=PA386 ''The Essential Guide to Primary Care Procedures''], p.386, Wolters Kluwer Health. {{ISBN|978-0-7817-7390-4}}.</ref>

== Epidemiology ==
Around 2% of the general population has a lipoma.<ref name=Kr2006 /> These tumors can occur at any age, but are most common in middle age, often appearing in people from 40 to 60 years old.<ref name=Salam>{{cite journal |author=Salam GA |title=Lipoma excision |journal=Am Fam Physician |volume=65 |issue=5 |pages=901–4 |date=March 2002 |pmid=11898962 |url=http://www.aafp.org/afp/20020301/901.html |access-date=2006-08-31 |archive-date=2008-05-11 |archive-url=https://web.archive.org/web/20080511190508/http://www.aafp.org/afp/20020301/901.html |url-status=dead }}</ref> Cutaneous lipomas are rare in children, but these tumors can occur as part of the inherited disease [[Bannayan-Zonana syndrome]].<ref>{{cite journal  |vauthors=Buisson P, Leclair MD, Jacquemont S, etal |title=Cutaneous lipoma in children: 5 cases with Bannayan-Riley-Ruvalcaba syndrome |journal=J. Pediatr. Surg. |volume=41 |issue=9 |pages=1601–3 |date=September 2006 |pmid=16952599 |doi=10.1016/j.jpedsurg.2006.05.013}}</ref><ref>{{cite journal |vauthors=Gujrati M, Thomas C, Zelby A, Jensen E, Lee JM |title=Bannayan-Zonana syndrome: a rare autosomal dominant syndrome with multiple lipomas and hemangiomas: a case report and review of literature |journal=Surg Neurol |volume=50 |issue=2 |pages=164–8 |date=August 1998 |pmid=9701122 |doi= 10.1016/S0090-3019(98)00039-1}}</ref>

Lipomas are usually relatively small with diameters of about 1–3&nbsp;cm,<ref name="webmd">[http://www.webmd.com/skin-problems-and-treatments/tc/lipoma-topic-overview Lipoma—topic overview] at webmd.com</ref> but in rare cases they can grow over several years into "giant lipomas" that are 10–20&nbsp;cm across and weigh up to 4–5&nbsp;kg.<ref>{{cite journal |vauthors=Hakim E, Kolander Y, Meller Y, Moses M, Sagi A |title=Gigantic lipomas |journal=Plast. Reconstr. Surg. |volume=94 |issue=2 |pages=369–71 |date=August 1994 |pmid=8041830 |doi=10.1097/00006534-199408000-00025}}</ref><ref>{{cite journal |vauthors=Terzioglu A, Tuncali D, Yuksel A, Bingul F, Aslan G |title=Giant lipomas: a series of 12 consecutive cases and a giant liposarcoma of the thigh |journal=Dermatol Surg |volume=30 |issue=3 |pages=463–7 |date=March 2004 |pmid=15008886 |doi=10.1111/j.1524-4725.2004.30022.x|s2cid=27990680 }}</ref>

== Other animals ==
Lipomas occur in many animals, but are most common in older dogs, particularly older [[Labrador Retriever]]s, [[Doberman Pinschers]], and [[Miniature Schnauzer]]s.<ref name=Merck /> Overweight female dogs are especially prone to developing these tumors, and most older or overweight dogs have at least one lipoma.<ref>[http://www.purinaone.com.au/Article/articledetails.aspx?id=753 Lipomas] {{Webarchive|url=https://web.archive.org/web/20080720194250/http://www.purinaone.com.au/Article/articledetails.aspx?id=753 |date=2008-07-20 }} Veterinary & Aquatic Services Department, Purina</ref><ref name=vt.edu>[http://education.vetmed.vt.edu/curriculum/vm8304/lab_companion/histo-path/introhistopath/Lab9/Lesions/lipoma.htm Lipoma] Virginia Polytechnic Institute and State University</ref> In dogs, lipomas usually occur in the trunk or upper limbs.<ref name=Merck>[http://merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/72220.htm Adipose Tissue Tumors] {{Webarchive|url=https://web.archive.org/web/20160304074602/http://merckvetmanual.com/mvm/index.jsp?cfile=htm%2Fbc%2F72220.htm |date=2016-03-04 }} The Merck Veterinary Manual, (9th ed.)</ref> They are also found less commonly in cattle and horses, and rarely in cats and pigs.<ref name=vt.edu /><ref>[http://vetmedicine.about.com/cs/dogdiseasesl/a/lipomas.htm Lipomas (Fatty Tumors)] {{Webarchive|url=https://web.archive.org/web/20080518093235/http://vetmedicine.about.com/cs/dogdiseasesl/a/lipomas.htm |date=2008-05-18 }} Veterinary Q & A</ref> However, a pedunculated lipoma can cause entrapment and torsion of the intestine in horses, causing necrosis, colic, and possibly death. The intestine becomes twisted around the stalk of the lipoma and loses blood supply.<ref>{{cite book|title=The Merck Veterinary Manual|edition=9th |date=2005|publisher=Merial|isbn=978-0-911910-50-6}}</ref>
{{Clear}}

== References ==
{{Reflist}}

== External links ==
{{Medical resources
|  DiseasesDB     = 7493
|  ICD10          = {{ICD10|D|17||d|10}} ([[ILDS]] D17.910)
|  ICD9           = {{ICD9|214}}
|  ICDO           = {{ICDO|8850|0}}
|  OMIM           =
|  MedlinePlus    = 003279
|  eMedicineSubj  = med
|  eMedicineTopic = 2720
|  eMedicine_mult = {{eMedicine2|derm|242}}
|  MeshID         = D008067
}}
{{Commons category}}

{{Diseases of the skin and appendages by morphology}}
{{Soft tissue tumors and sarcomas}}

[[Category:Dermal and subcutaneous growths]]
[[Category:Soft tissue disorders]]
[[Category:Benign neoplasms]]
[[Category:Soft tissue tumors]]
[[Category:Wikipedia medicine articles ready to translate]]