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Soft Tissue Tumors
Plexiform fibrohistiocytic tumor
Author: Nat Pernick, M.D., PathologyOutlines.com, Inc.
Reviewer: David Lucas, M.D., University of Michigan Health Systems (January 2009)
Revised: 26 June 2009, last major update June 2009
Definition
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● Dermal or subcutaneous, plexiform or multinodular proliferation of fibrohistiocytic cells and osteoclast-like giant cells with chronic inflammatory infiltrate
Terminology
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● First described in 1988 (Am J Surg Pathol 1988;12:818)
● Also called plexiform fibrous histiocytoma
● May have common histogenesis with cellular neurothekeoma (Am J Surg Pathol 2009;33:905)
Epidemiology
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● Usually children and young adults, 80% female
Clinical
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● Small, slow growing dermal or subcutaneous mass, often upper extremity (65%) or lower extremity (27%)
Case reports
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● 3 year old child whose tumor lacked osteoclast-like giant cells (Am J Dermatopathol 2002;24:399)
● 6 year old boy with small perioral tumor (Eur J Dermatol 2004;14:118)
● 24 year old woman with supraclavicular myxoid tumor without giant cells (Archives 2004;128:931)
● 39 year-old woman with a recurrent tumor (Univ Pittsburgh Case #316)
Treatment and prognosis
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● Low grade malignant behavior
● After excision, recurs locally, rarely has nodal or pulmonary metastases (Am J Surg Pathol 1999;23:662)
Gross description
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● Multinodular, poorly circumscribed, firm, dermal or subcutaneous, 3 cm or less
Micro description
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● Deep dermal or subcutaneous tumor with ray like extension into skeletal muscle or adipose tissue
● Overlying epidermis and dermis is usually normal
● Plexiform or multinodular proliferation of fibrohistiocytic cells with minimal atypia plus osteoclast-like giant cells and chronic inflammatory infiltrate
● Nodules or clusters are interconnected in characteristic plexiform arrangement
● Prominent dilated vessels; more sclerotic than MFH
● Often hemorrhage and hemosiderin
● Vascular invasion in 10-20%
● Usually 0-2 MF/10 HPF, no necrosis
● Subtypes are fibrohistiocytic (histiocyte-like cells and giant cells), fibroblastic (fibroblast-like cells) and mixed
Micro images
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Subcutaneous proliferation of bland fibrous tissue which radiates outward from center of lesion
Most tumors have nodules of Histiocyte-like cells have pale Nodules may be composed
histiocyte-like cells and giant staining cytoplasm; giant cells of cells with elongated nuclei
cells, also fibrous tissue and are also present
hemorrhage
Tumor with nodules and #2 Fibrous tissue may resemble
fibrous tissue #1 desmoid fibromatosis
Nodular and plexiform Nodule is composed of mononuclear cells
growth pattern and osteoclast-like giant cells
Axillary lymph node has Nodules are composed of Myxoid tumor without giant cells:
multiple plexiform nodules plump cells and multi- H&E, CD68 (fig 3), CD34 (fig 4)
within and outside the node nucleated giant cells
H&E, CD68 and vimentin Alpha smooth muscle actin Various images
stains tumor around nests
Various images Various images Various images
Virtual slides (USCAP)
Other images: 12 year old girl with upper arm lesion #1; #2; #3
Cytology description
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● Plump fibroblastic cells and histiocyte-like cells within a finely granular myxoid background
● Also osteoclast-like giant cells (Acta Cytol 1999;43:867)
Cytology images
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Various images
Positive stains
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● Vimentin, CD68 (giant cells and mononuclear histiocyte-like cells), smooth muscle actin (fibroblast-like cells, Histopathology 1991;19:503)
Negative stains
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● S100, keratin, CD45, Factor VIII, desmin
Electron microscopy
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● Resembles myofibroblasts, fibroblasts and undifferentiated cells
Differential Diagnoses
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● Benign fibrous histiocytoma - older patients, prominent foam cells, no plexiform extensions of fibrous tissue, no nodules of histiocyte like cells, no multinucleated giant cells
● Cellular neurothekeoma - uniform population of epithelioid cells, no distinct nodules of histiocytoid cells or osteoclast-like giant cells, (Am J Surg Pathol 2007;31:329), podoplanin+ (Am J Dermatopathol 2009;31:137)
● Fibromatosis - centered in muscle, diffusely infiltrative, no nodules
● Fibrous hamartoma of infancy - immature cells present, also myxoid stroma
● Giant cell tumor - infiltrative nodules of mixed giant cells and spindle cells, frequent mitotic figures
● Neurofibroma - no distinct nodules, S100+
Additional references
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● Ann Diagn Pathol 2007;11:313, Arch Pathol Lab Med 2007;131:1135, Stanford University
End of Soft Tissue Tumors > Plexiform fibrohistiocytic tumor
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