Soft Tissue Tumors - Pleomorphic lipoma / spindle cell lipoma

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Soft Tissue Tumors

Adipose tissue

Pleomorphic lipoma / spindle cell lipoma - general

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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● Subcutaneous tumor of back, shoulder or posterior neck with mature adipocytes, bland spindle cells, floret cells and collagen (Stanford University)

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 description
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● 16q or 13q abnormalities in 70%
● Frequently hypodiploid

Pleomorphic lipoma

General
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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 spindle cell lipoma
● No/rare lipoblasts, no prominent vascularity

Micro images
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Numerous pleomorphic and floret cells

Various images

Other images: pleomorphic lipoma

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, Diagn Cytopathol 2010;38:184)

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-

Spindle cell lipoma

General
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● Mature adipocytes, bland spindle cells with wispy eosinophilic cytoplasm in subcutaneous tissue of neck, back or shoulder (Stanford University)

Epidemiology
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● Rarely are multiple tumors (Am J Surg Pathol 1998;22:40)

Case reports
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● 51 year old woman with hypopharyngeal tumor (Int J Med Sci 2011;8:479)
● 53 year old man with intramuscular tumor of face (J Cutan Pathol 2009;36:70)
● 55 year old man with neck mass (Case of the Week #182)
● 63 year old man with supraclavicular mass (Int J Otolaryngol 2010;2010:942152)

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

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

Hemangiopericytic vascular pattern

Pseudoangiomatous appearance

Spindle cells have inconspicuous cytoplasm and small, slender, uniform nuclei

Spindle cells and collagen with few adipocytes

Various images

Various images

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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Breast tumor: H&E and CD34

Positive stains
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● Spindle cells - CD34, androgen receptors in men and usually women (Arch Pathol Lab Med 2008;132:81)
● Adipocytes - S100

Negative stains
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● Spindle cells - S100, desmin

Electron microscopy description
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● Spindled non-fat storing mesenchymal cells and mature lipocytes (Am J Surg Pathol 1981;5:435)

Molecular/cytogenetics description
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● Usually 16q abnormalities

Differential diagnosis
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● Cellular angiofibroma: vascular tumor, but similar cytogenetics (Cancer Genet Cytogenet 2007;177:131)
● Lipomatous hemangiopericytoma: staghorn vascular pattern
● Myxoid liposarcoma: lipoblasts and pleomorphic spindle cells, prominent plexiform vascular pattern, no thick collagen bundles, CD34-
● Neurofibroma: different morphology, no prominent adipose, strongly S100+
● Schwannoma: different morphology, no prominent adipose, strongly S100+
● Solitary fibrous tumor: patternless pattern, thin collagen fibers, no prominent adipose, CD99+, bcl2+, CD34+

End of Soft Tissue Tumors > Adipose tissue > Pleomorphic lipoma / spindle cell lipoma - general

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