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Soft Tissue Tumors

Normal white fat

 

Author: Nat Pernick, M.D., PathologyOutlines.com, Inc.

Reviewer: David Lucas, M.D., University of Michigan Health Systems (January 2009)

Revised: 26 June 2009, last major update June 2009

 

Terminology

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● Also called White Adipose Tissue (WAT); cells are called adipocytes

 

Pathophysiology

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● Main function is energy storage

● Triglycerides circulate in blood in form of chylomicrons; the enzyme lipoprotein lipase, produced by adipocytes and present on luminal surface of endothelium, converts triglycerides to free fatty acids; free fatty acids are taken up by adipocytes and converted to triacylglycerol, which is stored within cytoplasmic lipid droplet of adipocytes

● Adipocytes also secrete leptin and IL6, but their effects in humans are not well defined

● Stromal cells also convert androstenedione to estrone, the main source of estrogen in men and postmenopausal women

 

Sites

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● Subcutaneous, mediastinum, abdomen, retroperitoneum

 

Gross description

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● Homogeneous, yellow, greasy surface, faint fibrous septa

 

Micro description

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● Uniform large spherical cells up to 120 microns, in which lipid droplet pushes nucleus to periphery and deforms it to a thin crescent

● Cytoplasm usually has single, clearly delimited vacuole

● Cells are clear because cytoplasmic fat dissolves during tissue processing

● Nucleus may have central vacuole or Lochkern

● Very thin membranes are present between cells

 

Micro images

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White adipose tissue and                                                                White adipose tissue

vasculature                                                                                          microvessels

 

 

                                                                             

Adipocytes along arteriole in mesentery                                     Fat emboli in lung-Oil Red O stain

 

 

Virtual slide (Univ Iowa)

 

Other images:  mature adipose tissue with transparent cytoplasm and thin fibrovascular septa #1#2

 

Positive stains

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● Vimentin (nonspecific), S100 (primarily for mature adipocytes), calretinin (also stains lipoma and liposarcoma, Hum Path 2006;37:312)

● Oil red O and Sudan Black stain neutral fat (must use frozen tissue because tissue processing removes fat); Oil red O also stains most carcinomas

● Nile blue sulfate stains neutral fat pink-red, and stains fatty acids/phospholipids blue

Basement membrane is highlighted by PAS and reticulin

 

Negative stains

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● CD31, keratin, desmin, muscle specific actin

 

Electron microscopy

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Pre-adipocytes - spindle cells with abundant endoplasmic reticulum and small spherical mitochondria

Mature adipocyte - large lipid droplet flattens nucleus against cytoplasmic membrane, variable pinocytotic vesicles; capillaries are close to adipocyte basement membrane

 

Electron microscopy images

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Subcutaneous adipocytes

 

End of Soft Tissue Tumors > Normal white fat

 

 

 

This information is intended for physicians and related personnel, who understand that medical information is often imperfect, and must also be interpreted in the context of a patient's clinical data using reasonable medical judgment.  This website should not be used as a substitute for the advice of a licensed physician.

 

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