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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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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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