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*Lipoma is usually encapsulated.
*Lipoma is usually encapsulated.
*Focal hemorrhage or fat necrosis may also occur, but it is much less common than in liposarcomas.
*Focal hemorrhage or fat necrosis may also occur, but it is much less common than in liposarcomas.
[[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>]]
[[File:Angiomyolipoma-7.JPG|thumb|none|300px|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>]]
 
=== Microscopic pathology ===
=== Microscopic pathology ===
Microscopically, lipomas are formed from mature fat cells.
*There is no nuclear hyperchromasia.
*Lipoma is usually encapsulated and have a distinct lobulated pattern.
Lipomas differ little in microscopic appearance from the surrounding fat because they are composed of mature fat cells, but the cells vary slightly in size and shape and are somewhat larger ( Fig. 14-1B ). The nuclei are uniform, and it is important to note that there is an absence of nuclear . Subcutaneous lipomas are usually thinly encapsulated and have a distinct lobular configuration. All are well vascularized, but, under normal conditions, the vascular network is compressed by the distended lipocytes and is not clearly discernible. The rich vascularity of these tumors becomes apparent in atrophic lipomas in which the markedly reduced volume of the lipocytes reveals the intricate vascular network in the interstitial space.
<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>

Revision as of 20:39, 11 November 2019

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2]

Overview

Pathophysiology

  • 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.[1][2]
  • Rearrangements of chromosome 12 is the most commonly cytogentic abnormality.
  • The DDIT3 gene, located on the long arm of chromosome 12, has been suggested to paly a role in adipocytic differentiation.[3]
  • This gene encodes a protein family, known to be enhancer binding protein.
  • Members of this protein family are highly expressed in fat and are engaged in the growth arrest of fat cells.

Genetics

Genetic abnormalities associated with lipoma pathogenesis include:[4]

  • Translocations in 12q13-15
  • Interstitial deletions of 13q
  • Rearrangements in 6p21-23

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 differnet 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.
Angiomyolipoma Gross Pathology[6]

Microscopic pathology

Microscopically, lipomas are formed from mature fat cells.

  • There is no nuclear hyperchromasia.
  • Lipoma is usually encapsulated and have a distinct lobulated pattern.

Lipomas differ little in microscopic appearance from the surrounding fat because they are composed of mature fat cells, but the cells vary slightly in size and shape and are somewhat larger ( Fig. 14-1B ). The nuclei are uniform, and it is important to note that there is an absence of nuclear . Subcutaneous lipomas are usually thinly encapsulated and have a distinct lobular configuration. All are well vascularized, but, under normal conditions, the vascular network is compressed by the distended lipocytes and is not clearly discernible. The rich vascularity of these tumors becomes apparent in atrophic lipomas in which the markedly reduced volume of the lipocytes reveals the intricate vascular network in the interstitial space.

  • Histopathologic slide of renal angiomyolipoma. Nephrectomy specimen. H & E stain.[7]
    Histopathologic slide of renal angiomyolipoma. Nephrectomy specimen. H & E stain.[7]
  • Histopathologic slide of renal angiomyolipoma. Nephrectomy specimen. H & E stain.[7]
    Histopathologic slide of renal angiomyolipoma. Nephrectomy specimen. H & E stain.[7]
  • Histopathologic slide of renal angiomyolipoma. Nephrectomy specimen. H & E stain.[7]
    Histopathologic slide of renal angiomyolipoma. Nephrectomy specimen. H & E stain.[7]
  • Histopathologic image of renal angiomyolipoma. Nephrectomy specimen. HMB-45 immunostain.[7]
    Histopathologic image of renal angiomyolipoma. Nephrectomy specimen. HMB-45 immunostain.[7]

Immunohistochemistry

Lipomas may have following immunohistochemical markers:[8]

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. ↑ Image courtesy of Dr Andrew Ryan. Radiopaedia (original file [1]).[http://radiopaedia.org/licence Creative Commons BY-SA-NC
  7. ↑ 7.0 7.1 7.2 7.3 http://librepathology.org/wiki/index.php/Angiomyolipoma
  8. ↑ Fletcher, Christopher (2002). Pathology and genetics of tumours of soft tissue and bone. Lyon: IARC Press. ISBN 9283224132.


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