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{{Lipoma}}
{{Lipoma}}


{{CMG}}
{{CMG}} {{AE}} {{Sahar}}
 
==Overview==
==Overview==
Lipomas are circumscribed encapsulated soft masses, made nearly entirely of fat. Solid components may present in some cases.
Lipoma is formed from mature adipocyte cells and is histologically indistinguishable from [[fat tissue]]. Recent studies have observed [[Cytogenetics|cytogenetic]] abnormalities in 50-60% of lipomas, suggesting its role in the lipoma [[pathogenesis]]. Rearrangements of [[chromosome 12]] are the most commonly [[Cytogenetics|cytogenetic]] abnormality. In a [[cross-sectional]] appearance, the lipoma is pale yellow to orange and has a uniform greasy surface with a lobular pattern. The [[subcutaneous]] lipoma is usually encapsulated and has a distinct lobulated [[pattern]].
 
==Pathophysiology==
==Pathophysiology==
 
*<nowiki/>Lipoma is formed from mature [[adipocyte]]<nowiki/>s and is [[histologically]] indistinguishable from [[fat tissue]].
*Lipomas are defined as soft masses of adipose (fat) cells which are often encapsulated by a thin layer of fibrous tissue.  
*Recent studies have observed [[cytogenetic|cytogenet]]<nowiki/>[[cytogenetic|ic]] abnormalities in 50-60% of lipomas, suggesting its role in the lipoma [[pathogenesis]].<ref name="pmid1988102">{{cite journal |vauthors=Sreekantaiah C, Leong SP, Karakousis CP, McGee DL, Rappaport WD, Villar HV, Neal D, Fleming S, Wankel A, Herrington PN |title=Cytogenetic profile of 109 lipomas |journal=Cancer Res. |volume=51 |issue=1 |pages=422–33 |date=January 1991 |pmid=1988102 |doi= |url=}}</ref><ref name="pmid8744279">{{cite journal |vauthors=Weiss SW |title=Lipomatous tumors |journal=Monogr Pathol |volume=38 |issue= |pages=207–39 |date=1996 |pmid=8744279 |doi= |url=}}</ref>
*They are benign tumors of subcutaneous fat, not attached to the underlying fascia.
*Rearrangements of [[chromosome 12]] is the most commonly [[cytogenetic]] abnormality.
*Clinically, they often present in the cephalic part of the body, specifically in the head, neck, shoulders, and backs of patients, although they can less commonly be seen elsewhere, for example, the thighs.  
*The [[DDIT3 gene|DDIT3]] [[gene]], located on the long arm of [[chromosome 12]], has been suggested to play a role in [[Adipocyte|adipocytic]] differentiation.<ref name="pmid9624148">{{cite journal |vauthors=Adelmant G, Gilbert JD, Freytag SO |title=Human translocation liposarcoma-CCAAT/enhancer binding protein (C/EBP) homologous protein (TLS-CHOP) oncoprotein prevents adipocyte differentiation by directly interfering with C/EBPbeta function |journal=J. Biol. Chem. |volume=273 |issue=25 |pages=15574–81 |date=June 1998 |pmid=9624148 |doi=10.1074/jbc.273.25.15574 |url=}}</ref>
*The tumors typically lie in the subcutaneous tissues of patients.
*This [[gene]] encodes a protein family, known to be enhancer binding [[protein]].
*Lipomas can also arise in visceral organs such as stomach, liver, duodenum, colon, thyroid, adrenal glands, pancreas, and parathyroid glands.
*Members of this [[protein]] family are highly expressed in [[fat]] and are engaged in the [[growth]] arrest of [[fat cells]].
*Maxillofacial lipomas, including intralingual, parotid, orbitonasal, maxillary sinusoidal, and parapharyngeal space masses, have also been documented.
*Gynecologic lipomas may occur in the uterus, ovaries, and broad ligament.
*Involvement of the heart (causing ventricular tachycardia), superior vena cava, brain, and spinal cord may also occur.
*Bone and intrarticular involvement is also common.
*Mucosal lipoms in the gatsrointestnial tract can cause bleeding and intuscception.
*Lipomas are histologically characterized by mature fat cells with no cytologic atypia/hyperchromasia/pleomorphism.
*Lipoblasts can be seen in lipomas, but they do not exhibit cytologic atypia/hyperchromasia/pleomorphism.
*Lipoma can occur as a response to trauma or they can appear sporadically.
 
=== Genetics ===
=== Genetics ===
* Lipomas are mainly characterized by rearrangements of chromosome 12q13q15 with several partner chromosomes in approximately, especially chromosome 3<ref name="pmid18551755">{{cite journal| author=Ida CM, Wang X, Erickson-Johnson MR, Wenger DE, Blute ML, Nascimento AG et al.| title=Primary retroperitoneal lipoma: a soft tissue pathology heresy?: report of a case with classic histologic, cytogenetics, and molecular genetic features. | journal=Am J Surg Pathol | year= 2008 | volume= 32 | issue= 6 | pages= 951-4 | pmid=18551755 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=18551755  }} </ref>.
*[[Genetic]] abnormalities associated with lipoma [[pathogenesis]] include:<ref name="WillénÅkerman1998">{{cite journal|last1=Willén|first1=Helena|last2=Åkerman|first2=Måns|last3=Dal Cin|first3=Paola|last4=De Wever|first4=Ivo|last5=Fletcher|first5=Christopher D.M|last6=Mandahl|first6=Nils|last7=Mertens|first7=Fredrik|last8=Mitelman|first8=Felix|last9=Rosai|first9=Juan|last10=Rydholm|first10=Anders|last11=Sciot|first11=Raf|last12=Tallini|first12=Giovanni|last13=Van Den Berghe|first13=Herman|last14=Vanni|first14=Roberta|title=Comparison of Chromosomal Patterns with Clinical Features in 165 Lipomas: A Report of the CHAMP Study Group|journal=Cancer Genetics and Cytogenetics|volume=102|issue=1|year=1998|pages=46–49|issn=01654608|doi=10.1016/S0165-4608(97)00292-6}}</ref>
* Lipomas without 12q13q15 rearrangements frequently show rearrangements of chromosome 6p21.
**Translocations in 12q13-15
* Several lipoma fusion genes have been identified and the most common is LPP-HMGA2, product of the t(3;12)(q27-q28;q14-a15).
**Interstitial [[Deletion|deletions]] of 13q
 
**Rearrangements in 6p21-23
=== Gross pathology ===
=== Gross pathology ===
[[File:Angiomyolipoma-7.JPG|thumb|none|200px|Angiomyolipoma Gross Pathology<ref>Image courtesy of Dr Andrew Ryan. [http://www.radiopaedia.org Radiopaedia] (original file [http://radiopaedia.org/cases/angiomyolipoma-7]).[http://radiopaedia.org/licence Creative Commons BY-SA-NC</ref>]]
*[[Gross pathology]] of lipoma may differ depending on [[anatomical]] location.<ref>{{cite book | last = Miettinen | first = Markku | title = Modern soft tissue pathology : tumors and non-neoplastic conditions | publisher = Cambridge University Press | location = Cambridge New York | year = 2010 | isbn = 9780521874090 }}</ref>
*Subcutaneous lipoma appear as a a soft, well-circumscribed rounded [[mass]] with different size ranging from millimeters to 5 cm or more.
*Lipomas larger than 10 cm are not common.
*In [[cross-sectional]] appearance, the lipoma is pale yellow to orange and has a uniform greasy surface with a lobular [[pattern]].
*Lipoma is usually encapsulated.
*Focal [[hemorrhage]] or [[fat necrosis]] may also occur, but it is much less common than in [[Liposarcoma|liposarcomas]].
*[[Intramuscular]] lipomas are usually larger than [[subcutaneous]] lipomas and may be encapsulated or diffuse.<ref>{{cite book | last = Miettinen | first = Markku | title = Modern soft tissue pathology : tumors and non-neoplastic conditions | publisher = Cambridge University Press | location = Cambridge New York | year = 2010 | isbn = 9780521874090 }}</ref>
*Grayish streaks of [[fibrous tissue]] may also be seen in fibrolipoma which has a firmer texture compared to ordinary lipoma.
[[File:Lipoma 06.jpg|thumb|none|400px|Lipoma gross appearance<ref>Image courtesy of Sebastian E Valbuena, Greg A O'Toole and Eric Roulot, wikimedia commons</ref>]]
=== Microscopic pathology ===
*[[Microscopic|Microscopically]], lipomas are formed from mature [[fat cells]].<ref name="SimangoRamdial2000">{{cite journal|last1=Simango|first1=Stephen|last2=Ramdial|first2=Pratistadevi K.|last3=Madaree|first3=Anil|title=Subpectoral post-traumatic lipoma|journal=British Journal of Plastic Surgery|volume=53|issue=7|year=2000|pages=627–629|issn=00071226|doi=10.1054/bjps.2000.3396}}</ref>
*There is no [[nuclear]] hyperchromasia.
*[[Subcutaneous]] lipoma is usually encapsulated and have a distinct lobulated [[pattern]].
*[[Cystic]] like changes may also be seen in lipoma due to impaired [[blood]] supply.
*[[Infection]] or [[trauma]] may cause [[fat necrosis]] or local liquefaction of fat, which may appear with [[phagocytic]] cells and formation of lipid [[cysts]].
*A possible [[benign]] finding in lipoma is the collection of [[histiocytes]] and the [[vacuolization]] of the [[nucleus]].<ref>{{cite book | last = Miettinen | first = Markku | title = Modern soft tissue pathology : tumors and non-neoplastic conditions | publisher = Cambridge University Press | location = Cambridge New York | year = 2010 | isbn = 9780521874090 }}</ref>
*[[Intramuscular]] lipoma may be well-demarcated from the adjacent [[muscular tissue]] or have a diffuse [[pattern]] with alternating [[adipocytes]] and [[skeletal muscle]] cells.
[[File:Spindle cell lipoma -- intermed mag.jpg|thumb|left|200px|Histologic view of spindle cell lipoma<ref>wikimedia commons</ref>]]
[[File:Spindle Cell Lipoma (2275051876).jpg|thumb|center|400px|Histologic view of subcutaneous lipoma<ref>Pathological and histological images courtesy of Ed Uthman at flickr, wikimedia commons</ref>]]




=== Immunohistochemistry ===
*Lipomas may have following immunohistochemical markers:<ref>{{cite book | last = Fletcher | first = Christopher | title = Pathology and genetics of tumours of soft tissue and bone | publisher = IARC Press | location = Lyon | year = 2002 | isbn = 9283224132 }}</ref>
**[[Vimentin]]
**[[S-100 protein]]
**[[Leptin]]
=== Gallery ===
<gallery>
Image:Renal angiomyolipoma (1).jpg|Histopathologic slide of renal angiomyolipoma. Nephrectomy specimen. H & E stain.<ref name= aaa>http://librepathology.org/wiki/index.php/Angiomyolipoma</ref>
Image:Renal angiomyolipoma (1).jpg|Histopathologic slide of renal angiomyolipoma. Nephrectomy specimen. H & E stain.<ref name= aaa>http://librepathology.org/wiki/index.php/Angiomyolipoma</ref>
Image:Renal angiomyolipoma (2).jpg|Histopathologic slide of renal angiomyolipoma. Nephrectomy specimen. H & E stain.<ref name= aaa>http://librepathology.org/wiki/index.php/Angiomyolipoma</ref>
Image:Renal angiomyolipoma (3).jpg|Histopathologic slide of renal angiomyolipoma. Nephrectomy specimen. H & E stain.<ref name= aaa>http://librepathology.org/wiki/index.php/Angiomyolipoma</ref>
Image:Renal angiomyolipoma (4) HMB-45 immunostain.JPG|Histopathologic image of renal angiomyolipoma. Nephrectomy specimen. HMB-45 immunostain.<ref name= aaa>http://librepathology.org/wiki/index.php/Angiomyolipoma</ref>
</gallery>
==References==
==References==
{{reflist|2}}
{{reflist|2}}

Latest revision as of 18:13, 21 November 2019

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sahar Memar Montazerin, M.D.[2]

Overview

Lipoma is formed from mature adipocyte cells and is histologically indistinguishable from fat tissue. Recent studies have observed cytogenetic abnormalities in 50-60% of lipomas, suggesting its role in the lipoma pathogenesis. Rearrangements of chromosome 12 are the most commonly cytogenetic abnormality. In a cross-sectional appearance, the lipoma is pale yellow to orange and has a uniform greasy surface with a lobular pattern. The subcutaneous lipoma is usually encapsulated and has a distinct lobulated pattern.

Pathophysiology

Genetics

Gross pathology

  • Gross pathology of lipoma may differ depending on anatomical location.[5]
  • Subcutaneous lipoma appear as a a soft, well-circumscribed rounded mass with different size ranging from millimeters to 5 cm or more.
  • Lipomas larger than 10 cm are not common.
  • In cross-sectional appearance, the lipoma is pale yellow to orange and has a uniform greasy surface with a lobular pattern.
  • Lipoma is usually encapsulated.
  • Focal hemorrhage or fat necrosis may also occur, but it is much less common than in liposarcomas.
  • Intramuscular lipomas are usually larger than subcutaneous lipomas and may be encapsulated or diffuse.[6]
  • Grayish streaks of fibrous tissue may also be seen in fibrolipoma which has a firmer texture compared to ordinary lipoma.
Lipoma gross appearance[7]

Microscopic pathology

Histologic view of spindle cell lipoma[10]
Histologic view of subcutaneous lipoma[11]


Immunohistochemistry

Gallery

  • Histopathologic slide of renal angiomyolipoma. Nephrectomy specimen. H & E stain.[13]

    Histopathologic slide of renal angiomyolipoma. Nephrectomy specimen. H & E stain.[13]

  • Histopathologic slide of renal angiomyolipoma. Nephrectomy specimen. H & E stain.[13]

    Histopathologic slide of renal angiomyolipoma. Nephrectomy specimen. H & E stain.[13]

  • Histopathologic slide of renal angiomyolipoma. Nephrectomy specimen. H & E stain.[13]

    Histopathologic slide of renal angiomyolipoma. Nephrectomy specimen. H & E stain.[13]

  • Histopathologic image of renal angiomyolipoma. Nephrectomy specimen. HMB-45 immunostain.[13]

    Histopathologic image of renal angiomyolipoma. Nephrectomy specimen. HMB-45 immunostain.[13]

References

  1. ↑ Sreekantaiah C, Leong SP, Karakousis CP, McGee DL, Rappaport WD, Villar HV, Neal D, Fleming S, Wankel A, Herrington PN (January 1991). "Cytogenetic profile of 109 lipomas". Cancer Res. 51 (1): 422–33. PMID 1988102.
  2. ↑ Weiss SW (1996). "Lipomatous tumors". Monogr Pathol. 38: 207–39. PMID 8744279.
  3. ↑ Adelmant G, Gilbert JD, Freytag SO (June 1998). "Human translocation liposarcoma-CCAAT/enhancer binding protein (C/EBP) homologous protein (TLS-CHOP) oncoprotein prevents adipocyte differentiation by directly interfering with C/EBPbeta function". J. Biol. Chem. 273 (25): 15574–81. doi:10.1074/jbc.273.25.15574. PMID 9624148.
  4. ↑ Willén, Helena; Åkerman, Måns; Dal Cin, Paola; De Wever, Ivo; Fletcher, Christopher D.M; Mandahl, Nils; Mertens, Fredrik; Mitelman, Felix; Rosai, Juan; Rydholm, Anders; Sciot, Raf; Tallini, Giovanni; Van Den Berghe, Herman; Vanni, Roberta (1998). "Comparison of Chromosomal Patterns with Clinical Features in 165 Lipomas: A Report of the CHAMP Study Group". Cancer Genetics and Cytogenetics. 102 (1): 46–49. doi:10.1016/S0165-4608(97)00292-6. ISSN 0165-4608.
  5. ↑ Miettinen, Markku (2010). Modern soft tissue pathology : tumors and non-neoplastic conditions. Cambridge New York: Cambridge University Press. ISBN 9780521874090.
  6. ↑ Miettinen, Markku (2010). Modern soft tissue pathology : tumors and non-neoplastic conditions. Cambridge New York: Cambridge University Press. ISBN 9780521874090.
  7. ↑ Image courtesy of Sebastian E Valbuena, Greg A O'Toole and Eric Roulot, wikimedia commons
  8. ↑ Simango, Stephen; Ramdial, Pratistadevi K.; Madaree, Anil (2000). "Subpectoral post-traumatic lipoma". British Journal of Plastic Surgery. 53 (7): 627–629. doi:10.1054/bjps.2000.3396. ISSN 0007-1226.
  9. ↑ Miettinen, Markku (2010). Modern soft tissue pathology : tumors and non-neoplastic conditions. Cambridge New York: Cambridge University Press. ISBN 9780521874090.
  10. ↑ wikimedia commons
  11. ↑ Pathological and histological images courtesy of Ed Uthman at flickr, wikimedia commons
  12. ↑ Fletcher, Christopher (2002). Pathology and genetics of tumours of soft tissue and bone. Lyon: IARC Press. ISBN 9283224132.
  13. ↑ 13.0 13.1 13.2 13.3 http://librepathology.org/wiki/index.php/Angiomyolipoma


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