Soft Tissue Tumors - Chondroid lipoma

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Soft Tissue Tumors

Adipose tissue

Chondroid lipoma

Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 4 November 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
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● Benign tumor of mature adipocytes, lipoblasts and myxochondroid stroma
● Rare, slow growing, painless
● First described in 1993 (Am J Surg Pathol 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, rarely oral cavity
● 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)
● 38 year female with painless thigh mass (Indian J Pathol Microbiol 2009;52:284)
● 55 year old man with pelvic mass (Korean J Radiol 2008;9:563)
● 71 year old woman with trunk mass (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

Thigh mass

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)
● Complex nuclear outlines
● Usually prominent vasculature with variable wall thickness
● May have hemorrhage and fibrosis, eosinophilic fibrinous matrix
● 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)

Case #52

Various images

Virtual slides
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Virtual slide (USCAP)

Cytology description
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● Mature lipocytes and lipoblast-like cells within a chondromyxoid matrix (Arch Pathol Lab Med 2001;125:1224)

Cytology images
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Multiple fragments with focal adipose differentiation and chondroid myxoid 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 Pathol 1995;26:706)
● Collagen IV reactivity around tumor cells
● High expression of cyclin d1 (Sarcoma 2011;2011:638403)

Negative stains
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● EMA, HMB45, smooth muscle actin, Ki-67 (or low)

Electron microscopy description
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● Abundant intracytoplasmic lipid and glycogen and numerous pinocytotic vesicles, characteristic of white adipocytes (Am J Surg Pathol 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 Pathol 1995;26:706)

Molecular/cytogenetics description
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● t(11;16) - also in hibernoma (Am J Surg Pathol 1999;23:1300, Mod Pathol 1999;12:88)

Cytogenetics images
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t(11;16) plus other changes

Differential diagnosis
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● Lipoma with chondroid metaplasia: 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, Ann Diagn Pathol 2012;16:230

End of Soft Tissue Tumors > Adipose tissue > Chondroid lipoma

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