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Soft Tissue Tumors
Chondroid lipoma
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
Definition
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● Benign tumor of mature adipocytes, lipoblasts and myxochondroid stroma
● Rare, slow growing, painless, benign mass
● First described as a distinct entity in 1993 (AJSP 1993;17:1103)
Epidemiology
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● 80% female; median age 36 years, range 14 to 70 years
Sites
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● Proximal extremities and limb girdles
● Intramuscular or subcutaneous
Case reports
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● 7 year old boy with thigh mass (Indian J Pathol Microbiol 2008;51:541)
● 33 year old man with hand mass (Case of the Week #52)
● 55 year old man with pelvic mass (Korean J Radiol 2008;9:563)
● Oral cavity (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2005;99:331)
● Trunk (Skeletal Radiol 2004;33:666)
● Incidental finding at hip replacement surgery (J Surg Orthop Adv 2004;13:42)
Treatment and prognosis
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● Excision is curative
● Does not recur, metastasize or transform
Gross description
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● Median 4 cm, up to 11 cm, encapsulated, yellow or white
Gross images
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Well circumscribed mass Lipomatous (arrows) and chondroid (*) areas
Well circumscribed tumor
Other images: yellow tumor
Micro description
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● Well circumscribed, nests and cords of small to medium, multivacuolated cells resembling lipoblasts, chondroblasts or hibernoma cells within a prominent chondromyxoid matrix with variable mature fat, rarely metaplastic bone (Skeletal Radiol 2008;37:475)
● Usually prominent vasculature with variable wall thickness
● May have hemorrhage and fibrosis
● No pleomorphism, no atypia, no/rare mitotic activity, no mature hyaline cartilage
Micro images
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Well circumscribed tumor Clusters of small to medium cells with vacuolated cytoplasm
Mature fat cells are present Mature fat cells (*), lipoblast-like cells (arrowheads)
and chondroid tissue (C)
Mature fat and chondroid tissue
Case #52 - Low power Medium power Medium power
Medium power High power
High power High power
Virtual slide (USCAP)
Cytology description
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● Mature lipocytes and lipoblast-like cells within a chondromyxoid matrix (Archives 2001;125:1224)
Cytology images
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Cell block shows multiple fragments with focal adipose differentiation
and chondromyxoid appearance
Positive stains
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● S100 (mature adipocytes stain stronger than lipoblasts) and vimentin, PAS+ glycogen, Alcian blue and toluidine blue (stain chondroitin substrate)
● Variable focal CD68 and keratin (Hum Path 1995;26:706)
Negative stains
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● EMA, HMB45, smooth muscle actin, Ki-67 (or low)
Electron microscopy
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● Abundant intracytoplasmic lipid and glycogen and numerous pinocytotic vesicles, characteristic of white adipocytes (AJSP 1995;19:1272)
● Resembles embryonal fat, and to a lesser extent, embryonal cartilage
● Cells have knob like protrusions of cell membrane containing granular, amorphous and fibrillar material
● No prominent mitochondria, no lysosomes (Hum Path 1995;26:706)
Molecular / cytogenetics
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● t(11;16) - also in hibernoma (AJSP 1999;23:1300, Mod Path 1999;12:88)
Cytogenetics images
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t(11;16) plus other changes
Differential Diagnoses
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● Chondroid metaplasia in a lipoma - true cartilage present
● Extraskeletal chondroma - distal extremities, mature hyaline cartilage, no fat
● Extraskeletal myxoid chondrosarcoma - prominent fibrous septa; chondroblasts typically lack intracytoplasmic vacuoles, no mature fat; frequently has mitotic figures and necrosis
● Mixed tumor - foci of epithelial differentiation, keratin+, no lipoblasts
● Myxoid liposarcoma - different sites, usually no prominent cords or clusters of cells; has delicate plexiform capillary matrix, t(12;16)
Additional references
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● Radiographics 2004;24:1433, Stanford University
End of Skin / Soft Tissue Tumors > Chondroid lipoma
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