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Soft Tissue Tumors
Pleomorphic lipoma / spindle cell lipoma - general
(see also pleomorphic lipoma, spindle cell lipoma below)
Author: Nat Pernick, M.D., PathologyOutlines.com, Inc.
Reviewer: David Lucas, M.D., University of Michigan Health Systems (January 2009)
Revised: 1 July 2010, last major update June 2009
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● Subcutaneous tumor of back, shoulder or posterior neck, usually men, with mature adipocytes, bland spindle cells, floret cells and collagen
Epidemiology
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● Pleomorphic lipoma and spindle cell lipoma represent a continuum of benign tumors - most tumors show some features of both
● 70% occur in subcutaneous tissue of shoulder, back and posterior neck
● 90% men; usually ages 45-65 years
● Usually relatively superficial
● If deep, some suggest calling well differentiated liposarcoma
Treatment and prognosis
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● Excision; only rare local recurrences, no metastases
Gross description
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● Usually 3-5 cm, well circumscribed, yellow-gray-white, firmer than classic lipoma
Molecular / cytogenetics
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● 16q or 13q abnormalities in 70%
● Frequently hypodiploid
Definition
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● Mature adipocytes, dense collagen and floret giant cells in subcutaneous tissue of neck, back or shoulder
● Usually dermal or beneath mucous membranes
Epidemiology
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● Rare - incidence is only 10% that of spindle cell lipoma
Treatment and prognosis
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● Excision, only rarely recurs
Micro description
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● Circumscribed tumor with adipocytes that are variable in size at low power
● Prominent floret giant cells (hyperchromatic, multinucleated, wreath like nuclei) and small round hyperchromatic cells
● May have spindle cells similar to those in spindle cell lipoma
● No/rare lipoblasts, no prominent vascularity
Micro images
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Numerous pleomorphic and floret cells
Cytology description
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● Atypical large and floret cells with background of mature adipocytes (Diagn Cytopathol 2005;32:110)
● Cells may appear malignant (Acta Cytol 2000;44:255)
Positive stains
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● CD34, vimentin
Negative stains
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● Keratin, S100 (fat cells are S100+), CD68, desmin, smooth muscle actin
Differential diagnosis
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● Neurofibroma - may have floret cells (Diagn Pathol 2007;2:47)
● Well differentiated liposarcoma - deep location, more lipoblasts, variable thick collagen, variable floret giant cells, CD34-
Additional references
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Definition
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● Mature adipocytes, bland spindle cells with wispy eosinophilic cytoplasm in subcutaneous tissue of neck, back or shoulder
Epidemiology
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● Rarely are multiple tumors (AJSP 1998;22:40)
Case reports
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● 53 year old man with intramuscular tumor of face (J Cutan Pathol 2009 Jan 27 [Epub ahead of print])
● 55 year old man with neck mass (Case of the Week #182)
Treatment and prognosis
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● Excision, only rarely recurs (Cancer 1975;36:1852)
Gross images
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Fatty (F) and hemorrhagic (H) tumor Yellow tumor due to numerous adipocytes
Other images: Breast tumor
Micro description
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● Mixture of mature adipocytes and bland spindle cells (pale eosinophilic cytoplasm with uniform wavy nuclei similar to neurofibroma) in mucinous / myxoid or fibrous background with thick collagen bundles
● Spindle cells are arranged in short fascicles with occasional nuclear palisading
● May have hemangiopericytic or angiomatous vascular pattern (Pathol Int 2007;57:26)
● May have minimal/no fat (Am J Dermatopathol 2007;29:437)
● Variable mast cells and lymphocytes
● No storiform pattern, no lipoblasts, no/rare mitotic activity
Micro images
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Adipocytes, spindle cells and ropy collagen
Pseudoangiomatous appearance Hemangiopericytic vascular pattern
Spindle cells are Spindle cells have inconspicuous cytoplasm
within fibrous bands and small, slender, uniform nuclei
Spindle cells and collagen with few adipocytes
H&E and androgen Male breast tumor
receptor staining
Cytology description
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● Scattered clusters of mildly pleomorphic spindle cells mixed with mature adipocytes, mast cells and small collagen fragments (Diagn Cytopathol 2000;23:362)
Cytology images
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Parotid tumor Breast tumor: H&E and CD34
Positive stains
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● Spindle cells - CD34, androgen receptors in men and usually women (Archives 2008;132:81)
● Adipocytes - S100
Negative stains
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● Spindle cells - S100, desmin
Electron Microscopy
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● Spindled non-fat storing mesenchymal cells and mature lipocytes (AJSP 1981;5:435)
Molecular / cytogenetics
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● Usually 16q abnormalities
Differential Diagnoses
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● Schwannoma - different morphology, no prominent adipose, strongly S100+
● Neurofibroma - different morphology, no prominent adipose, strongly S100+
● Solitary fibrous tumor - patternless pattern, thin collagen fibers, no prominent adipose, CD99+, bcl2+, CD34-
● Lipomatous hemangiopericytoma - staghorn vascular pattern
● Cellular angiofibroma - vascular tumor, but similar cytogenetics (Cancer Genet Cytogenet 2007;177:131)
● Myxoid liposarcoma - lipoblasts and pleomorphic spindle cells, prominent plexiform vascular pattern, no thick collagen bundles, CD34-
Additional references
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End of Soft Tissue Tumors > Pleomorphic lipoma / spindle cell lipoma
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