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Soft tissue Tumors

Fibroblastic / myofibroblastic tumors

Desmoplastic fibroblastoma


Reviewer: Komal Arora, M.D. (see Reviewers page)
Revised: 19 July 2012, last major update July 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
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● Fibroblastic lesion centered in subcutaneous tissue with reactive fibroblasts, low cellularity and abundant collagen (Hum Pathol 1998;29:676)
● Also called collagenous fibroma

Sites:
● Usually upper extremities, back, feet

Epidemiology
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● Rare benign lesion of adult men (70% between ages 40 and 69 years)

Case reports
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● 41 year old woman with thigh mass (J Cutan Pathol 2008;35 Suppl 1:70)

Treatment
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● Conservative excision, does not recur or metastasize

Gross description
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● Usually 1-4 cm, well circumscribed, may be lobulated, has firm and homogeneous gray cut surface resembling cartilage

Gross images
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Well circumscribed tumor

Micro description
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● Paucicellular, bland spindled (stellate) and reactive appearing fibroblasts and myofibroblasts separated by abundant collagen with variable myxoid stroma
● Fibroblasts have amphophilic cytoplasm, vesicular nuclei and distinct nucleoli
● 70% of cases involve subcutis, 25% extend into skeletal muscle

Micro images
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Large, reactive appearing spindled fibroblasts in fibrous matrix


Focus of low cellularity and dense collagen


More cellular area with reactive type fibroblasts


Scattered stellate cells in hypovascular collagenous matrix;


Hypocellular lesion with pseudocapsule and sparse cells separated by abundant collagen


Spindle cells with long nuclei in dense collagenous stroma;


Vimentin+


Most cells are negative for smooth muscle actin

Positive stains
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● Vimentin, variable alpha smooth muscle actin

Negative stains
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● Desmin, EMA, S100, CD34

Electron microscopy description
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● May have fibronexus junctions-markers of myofibroblastic differentiation (Ultrastruct Pathol 2004;28:149)

Molecular
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● t(2;11)(q31;q12) or 11q12 abnormalities observed rarely (Cancer Genet Cytogenet 2004;149:161, Cancer Genet 2011;204:569, Histopathology 2007;51:859, Cancer Genet Cytogenet 2009;192:73)

Differential diagnosis
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Fibromatosis: not circumscribed, more cellular, fascicular pattern, prominent vasculature (Adv Anat Pathol 1999;6:275)

Additional references
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Am J Surg Pathol 1995;19:1077, APMIS 2002;110:283, Stanford University

End of Soft Tissue Tumors > Fibroblastic / myofibroblastic tumors > Desmoplastic fibroblastoma


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