Lipoma

Lipoma
	Diagnosis in short
	; Mature adipose tissue (lipoma). H&E stain.
Synonyms	steatoma (old term, ambiguous)
LM	mature adipocytes
LM DDx	liposarcoma, benign fat
IHC	S-100 +ve
Molecular	MDM2/CDK4 amplification absent
Gross	soft yellow tissue - typically with a thin capsule and lobulated
Site	soft tissue
Prevalence	common
Prognosis	benign
Treatment	surgical removal or follow-up

Lipoma is a benign adipocytic tumour.

General

Benign.
Several variants exist.
- Angiolipoma - one of the (classically) painful skin lesions.
May be seen in association with MERRF syndrome (myoclonic epilepsy with ragged-red fibres).^[1]

Gross

Soft yellow tissue - typically lobulated and with a very thin capsule.

Note:

May be quite large ~10 cm.
Thigh lesions are more likely to the malignant than other sites.^[2]

Microscopic

Features:

Collection of mature adipocytes.
- Variation of size may be seen -- should prompt a search for lipoblasts.^[3]

Notes:

Microscopically not definitely distinguishable from mature clump of fat.
- The lesion must be labeled lipoma (by the clinican) to be signed-out as such.

DDx:

Liposarcoma - increased number of blood vessels,^[4] esp. chickenwire-like vessels, fibrous septae.
Benign adipose tissue.

Images:

Lipoma - cardiac (ahajournals.org).^[5]

Variants

Angiolipoma

A painful skin lesion.

Microscopic:

Numerous blood vessels present.
+/-Microthrombi.

DDx:

Liposarcoma.

Myolipoma

General:

May mimic a sarcoma radiologically.^[6]
Extremely rare.^[7]
Usually large ~ 16 cm.^[8]

Microscopic:^[7]

Mature adipose tissue.
Benign smooth muscle - usually ~ 2x amount of fat.

Note:

If skeletal muscle is present consider intramuscular lipoma.^[9]

IHC:^[7]

Actin +ve.
Desmin +ve.

Images:

Images

Lipoma - intermed. mag.
Lipoma - high mag.
Mature fat. (WC)

Molecular

MDM2/CDK4 gene amplification absent.
- Testing suggested in lesions greater than 10 cm, thigh lesions and lesions with cytologic atypia.^[2]

Sign out

Large lesion looks like lipoma

Bland lesion >10 cm may be well-differentiated liposarcoma.^[11]

Lesion (Submitted as "Lipoma"), Right Neck, Excision:
	- Bland appearing adipose tissue suggestive of lipoma, see comment.
	- One benign lymph node.

Comment:
Due to the size of the lesion, the case will be sent to a soft tissue pathologist for review.

Block letter

SUBCUTANEOUS TISSUE ("LIPOMA"), LEFT AXILLA, EXCISION: 
- MATURE ADIPOSE TISSUE CONSISTENT WITH LIPOMA.

LESION ("LIPOMA"), SPERMATIC CORD (LATERALITY NOT SPECIFIED), EXCISION: 
- MATURE ADIPOSE TISSUE CONSISTENT WITH LIPOMA.

Colonic lipoma (clinically suspected)

B. SIGMOID COLON AT 55 CM, BIOPSY:
- COLORECTAL-TYPE MUCOSA WITHIN NORMAL LIMITS WITH A SMALL AMOUNT OF SUBMUCOSAL
  ADIPOSE TISSUE; COMPATIBLE WITH CLINICAL IMPRESSION OF LIPOMA.

Mirco

The sections show mature adipocytes. There is no increase in vascularity. No thick fibrous septa are present.

References

↑ Jones, AP.; Lewis, CJ.; Dildey, P.; Hide, G.; Ragbir, M. (Jan 2012). "Lipoma or liposarcoma? A cautionary case report.". J Plast Reconstr Aesthet Surg 65 (1): e11-4. doi:10.1016/j.bjps.2011.08.004. PMID 21865105.
↑ ^2.0 ^2.1 Wong, DD.; Low, IC.; Peverall, J.; Robbins, PD.; Spagnolo, DV.; Nairn, R.; Carey-Smith, RL.; Wood, D. (Apr 2016). "MDM2/CDK4 gene amplification in large/deep-seated 'lipomas': incidence, predictors and clinical significance.". Pathology 48 (3): 203-9. doi:10.1016/j.pathol.2016.02.007. PMID 27020493.
↑ Mentzel, T.; Fletcher, CD. (1995). "Lipomatous tumours of soft tissues: an update.". Virchows Arch 427 (4): 353-63. PMID 8548119.
↑ Yang, YJ.; Damron, TA.; Cohen, H.; Hojnowski, L. (Oct 2001). "Distinction of well-differentiated liposarcoma from lipoma in two patients with multiple well-differentiated fatty masses.". Skeletal Radiol 30 (10): 584-9. doi:10.1007/s002560100395. PMID 11685482.
↑ Friedberg, MK.; Chang, IL.; Silverman, NH.; Ramamoorthy, C.; Chan, FP. (May 2006). "Images in cardiovascular medicine. Near sudden death from cardiac lipoma in an adolescent.". Circulation 113 (21): e778-9. doi:10.1161/CIRCULATIONAHA.105.589630. PMID 16735681. http://circ.ahajournals.org/content/113/21/e778.full.
↑ URL: http://www.webmedcentral.com/article_view/1878. Accessed on: 14 March 2013.
↑ ^7.0 ^7.1 ^7.2 Murphey, MD.; Carroll, JF.; Flemming, DJ.; Pope, TL.; Gannon, FH.; Kransdorf, MJ.. "From the archives of the AFIP: benign musculoskeletal lipomatous lesions.". Radiographics 24 (5): 1433-66. doi:10.1148/rg.245045120. PMID 15371618. http://radiographics.rsna.org/content/24/5/1433.long.
↑ Meis, JM.; Enzinger, FM. (Feb 1991). "Myolipoma of soft tissue.". Am J Surg Pathol 15 (2): 121-5. PMID 1703396.
↑ URL: http://surgpathcriteria.stanford.edu/softfat/lipoma/intramuscular_lipoma.html. Accessed on: 14 March 2013.
↑ Lee, YS.; Park, SE.; Lee, JU.; Choi, ES.. "MRI of a subcutaneous myolipoma in the ankle: a case report.". Korean J Radiol 12 (5): 641-5. doi:10.3348/kjr.2011.12.5.641. PMC 3168809. PMID 21927569. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3168809/.
↑ URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3422587/. Accessed on: 3 June 2017.

[pmid21865105-1] Jones, AP.; Lewis, CJ.; Dildey, P.; Hide, G.; Ragbir, M. (Jan 2012). "Lipoma or liposarcoma? A cautionary case report.". J Plast Reconstr Aesthet Surg 65 (1): e11-4. doi:10.1016/j.bjps.2011.08.004. PMID 21865105.

[pmid27020493-2] 2.0 ^2.1 Wong, DD.; Low, IC.; Peverall, J.; Robbins, PD.; Spagnolo, DV.; Nairn, R.; Carey-Smith, RL.; Wood, D. (Apr 2016). "MDM2/CDK4 gene amplification in large/deep-seated 'lipomas': incidence, predictors and clinical significance.". Pathology 48 (3): 203-9. doi:10.1016/j.pathol.2016.02.007. PMID 27020493.

[pmid8548119-3] Mentzel, T.; Fletcher, CD. (1995). "Lipomatous tumours of soft tissues: an update.". Virchows Arch 427 (4): 353-63. PMID 8548119.

[pmid11685482-4] Yang, YJ.; Damron, TA.; Cohen, H.; Hojnowski, L. (Oct 2001). "Distinction of well-differentiated liposarcoma from lipoma in two patients with multiple well-differentiated fatty masses.". Skeletal Radiol 30 (10): 584-9. doi:10.1007/s002560100395. PMID 11685482.

[pmid16735681-5] Friedberg, MK.; Chang, IL.; Silverman, NH.; Ramamoorthy, C.; Chan, FP. (May 2006). "Images in cardiovascular medicine. Near sudden death from cardiac lipoma in an adolescent.". Circulation 113 (21): e778-9. doi:10.1161/CIRCULATIONAHA.105.589630. PMID 16735681. http://circ.ahajournals.org/content/113/21/e778.full.

[6] URL: http://www.webmedcentral.com/article_view/1878. Accessed on: 14 March 2013.

[pmid15371618-7] 7.0 ^7.1 ^7.2 Murphey, MD.; Carroll, JF.; Flemming, DJ.; Pope, TL.; Gannon, FH.; Kransdorf, MJ.. "From the archives of the AFIP: benign musculoskeletal lipomatous lesions.". Radiographics 24 (5): 1433-66. doi:10.1148/rg.245045120. PMID 15371618. http://radiographics.rsna.org/content/24/5/1433.long.

[pmid1703396-8] Meis, JM.; Enzinger, FM. (Feb 1991). "Myolipoma of soft tissue.". Am J Surg Pathol 15 (2): 121-5. PMID 1703396.

[9] URL: http://surgpathcriteria.stanford.edu/softfat/lipoma/intramuscular_lipoma.html. Accessed on: 14 March 2013.

[pmid21927569-10] Lee, YS.; Park, SE.; Lee, JU.; Choi, ES.. "MRI of a subcutaneous myolipoma in the ankle: a case report.". Korean J Radiol 12 (5): 641-5. doi:10.3348/kjr.2011.12.5.641. PMC 3168809. PMID 21927569. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3168809/.

[11] URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3422587/. Accessed on: 3 June 2017.

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