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Skin / Soft Tissue Tumors

Benign fibrous histiocytoma (superficial)

 

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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● Storiform pattern of bland spindle cells and foamy histiocytes centered in dermis with possible extension to subcutis

● Variable hemosiderin, multinucleated giant cells, chronic inflammatory cells and pseudoepitheliomatous hyperplasia

 

Terminology

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● Also called dermatofibroma (particularly if sclerotic and hypocellular), dermal fibrous histiocytoma

● Part of WHO classification for skin tumors, not soft tissue tumors

● See also Bone, Eye-Conjunctiva, Eye-Orbit and Heart chapters

● See also variants described separately - aneurysmal,  angiomatoid,  atypical,  cellular,  epithelioid,  juvenile xanthogranuloma

 

Epidemiology

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● Very common benign, indolent tumor of adults, common site is legs of women 20-50 years old

● May be associated with trauma

● Line of differentiation is uncertain

● Multiple lesions may be associated with immunosuppression (Int J Dermatol 2008;47:723)

 

Pathophysiology

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● Fibroblasts cause strong expression of keratin 19 by keratinocytes and production of a galectin-1-rich extracellular matrix, which may account for pseudoepitheliomatous hyperplasia (J Dermatol Sci 2009;55:18)

 

Treatment and prognosis

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● Excision; local recurrence is rare even with involved margins

● Rarely is locally aggressive or metastatic (more common for facial lesions, with extension into subcutis)

 

Gross description

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● Tan-brown, firm, mobile, painless papule < 2 cm in dermis

● Size varies slightly with time; rarely > 5 cm and plaque-like (Australas J Dermatol 2008;49:106)

● May dimple upon lateral compression; may have overlying scaling

 

Gross images

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Inward dimpling due to tumor                         Dimpling when squeezed

binding to subcutis (arrow)                             along its margins

Source: UAB                                                        Source: UCSF

 

Dermoscopy description

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● Wide range of presentations (Arch Dermatol 2008;144:75)

● Pigment network (72%, 3% are atypical), white scar-like patch (57%), different vascular structures (50%), white network (18%)

● May resemble melanoma

 

Dermoscopy images

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http://www.dermoscopy.co.uk/imgs/gallery/figure4.jpg                                        [DF2.jpg]

Pseudonetwork present                                  Central white scar-like patch surrounded by a

pigmented network and many brown globules.

 

 

Figure 1                    Figure 2

Different patterns                                               Various images 

 

 

Figure 3                     Figure 4

Various images                                                  Various patterns

 

 

Figure 5                     Figure 6

Vascular structures                                          Other structures

 

Micro description

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● Well defined but non-encapsulated

● Storiform pattern of spindled and bland fibroblasts and histiocyte-like cells in mid-dermis and subcutaneous tissue with infiltrative margins but sparing epidermis

● Spindle cells have scant cytoplasm, thin elongated nuclei with pointed ends

● Nuclei almost touch each other, unlike smooth muscle lesions

● Also foamy histiocytes with variable hemosiderin, some multinucleated giant cells, branching vessels, chronic inflammatory cells, pseudoepitheliomatous hyperplasia and epidermal hyperpigmentation

● Often Touton giant cells (superficial and filled with hemosiderin)

● 2% have 4 or more mitotic figures/10 HPF, but still benign behavior (J Cutan Pathol 2008;35:839)

● See also variants described separately - aneurysmal,  angiomatoid,  atypical,  cellular,  epithelioid,  juvenile xanthogranuloma

● Rare variants are balloon cell (Am J Dermatopathol 2007;29:197), signet ring (Am J Dermatopathol 2009;31:84)

 

Micro images

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Tumor is more basophilic                                Basophilia is due                                 

than surrounding dermis                                 to increased cellularity                    

 

 

                                                        

Sharp border between                                      Tumor cells are composed            

tumor and subcutis                                           of histiocyte-like cells and foam cells

 

 

                                                      

Tumor cells are mostly                                     Fat may be entrapped at edge,

fibrous in this focus                                           but must differentiate from infiltration of DFSP

 

 

                                                                                                        

Randomly arranged foam cells,                     Foam cells vary from none (top),   

fibroblasts and histiocyte-like cells;             mixed (middle) to predominating (bottom)                 

foam cells are somewhat                                               

specific for this lesion

 

 

                                                                            

Less common finding of                                   Epithelial hyperplasia-left side shows

predominately foam cells                                squamous / basaloid differentiation,            

and cholesterol clefts                                       right side shows follicular differentiation   

 

 

                                

Cellularity changes over time                         Vulvar tumor has uniform spindle cells

from subtle increase in                                    confined to dermis

fibroblasts (fig A) to cellular           

tumor (fig B/C) to sclerotic Lesion

(fig D-right side)

 

 

Benign fibrous histiocytoma. This lesion is associated with basaloid proliferation of the overlying skin. This change does not represent a basal cell carcinoma.                                                           Benign fibrous histiocytoma of skin. The tumor is mainly composed of hemosiderin-laden macrophages.                                                                 

Pseudoepitheliomatous                                   Marked hemosiderin-laden            

hyperplasia                                                          macrophages                                     

 

 

i1543-2165-130-6-831-f01               

Low Ki-67 compared to DFSP and AFX

 

Other images: tumor with hyperplastic epithelium #1;  #2;  hyperplastic epidermis and sclerotic stroma #1;  #2;  #3;  foam cells with vacuolated cytoplasm;  fibroblastic cells with vacuolated cytoplasm in collagenous stroma;  spindle cell nodule;  paucicellular dermal tumor;  spindle cells in dense collagenous stroma

 

Positive stains

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● Vimentin, Factor XIIIa

● Also tenascin at dermoepidermal junction (Hum Path 2001;32:50); variable calponin (65%), actin, desmin, myosin

 

Negative stains

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● CD68, CD34, bcl2

● Ki-67 < 10% (Archives 2006;130:831)

 

Molecular / cytogenetics

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● Often clonal

 

Differential diagnosis

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● Atypical fibroxanthoma - characteristic gross appearance, storiform pattern not prominent, marked pleomorphism

● Dermatofibrosarcoma protuberans - “tight” storiform pattern, infiltrative, more cellular, no foam cells, CD34+

● Kaposi’s sarcoma - vascular tumor with red blood cell extravasation

● Leiomyoma or leiomyosarcoma - confusion based primarily on variable staining of benign fibrous histiocytoma for muscle markers

● Malignant fibrous histiocytoma - infiltrative, marked pleomorphism and mitotic activity

● Rosai-Dorman disease - CD68+ histiocytes, not storiform

 

 

End of Skin / Soft Tissue Tumors > Benign fibrous histiocytoma (superficial)

 

 

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