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Skin / Soft Tissue Tumors

Atypical fibrous histiocytoma

 

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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● Cellular, circumscribed dermal lesion of spindled fibroblasts, myofibroblasts, histiocyte-like cells and often giant cells

● Marked nuclear pleomorphism and mitotic figures (often atypical)

● No tumor cell necrosis

● No vascular invasion

 

Terminology

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● Rare variant of cutaneous fibrous histiocytoma

● Also called pseudosarcomatous fibrous histiocytoma or dermatofibroma with monster cells

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

● First described in 1983 (J Cutan Pathol 1983;10:327)

 

Epidemiology

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● Median age 38 years (range 5-79 years), no gender preference

 

Sites

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● Solitary lesions usually arise on extremities or trunk (Am J Dermatopathol 1986;8:467)

● Also head and neck, vulva

 

Case reports

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● 25 year old woman with recurrent leg lesion (Eur J Dermatol 1998;8:122)

62 year old woman with leg lesion (Tokai J Exp Clin Med 2004;29:49)

64 year old woman with 3 cm back lesion (Am J Dermatopathol 2002;24:36)

79 year old woman with leg lesion (Am J Dermatopathol 1997;19:312)

90 year old man with scrotal lesion (Ann Diagn Pathol 2003;7:370)

 

Treatment and prognosis

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● May be misdiagnosed as sarcoma (Histopathology 1990;17:167)

● Complete excision with negative margins

● Occasional local recurrence (14%) or distant metastasis (AJSP 2002;26:35)

 

Gross description

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● Median 1.5 cm (0.4 to 8 cm), nodular or polypoid

 

Micro description

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● Involvement of dermis and superficial subcutaneous tissue by pleomorphic, plump, spindle or polyhedral cells with large hyperchromatic, irregular or bizarre nuclei

● Background of classic fibrous histiocytoma including spindle cells with storiform pattern and entrapped thick collagen bundles, especially at the periphery

● Variable multinucleated giant cells, often with bizarre nuclei (“monster cells”, Am J Dermatopathol 1987;9:380) and foamy or hemosiderin-rich cytoplasm

● 0-15 mitotic figures/10 HPF, frequently atypical

● Necrosis occasionally present

 

Micro images

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Enlarged cells with hyperchromatic nuclei, but no / rare mitotic figures (source: AFIP Fascicle, 3rd series)

 

Positive stains

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● Vimentin, CD34 (occasionally)

 

Negative stains

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● CD68, S100, keratin (MNF116), EMA; <1% positive for MIB1 (Am J Dermatopathol 2004;26:367)

 

Differential diagnosis

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● Atypical fibroxanthoma - sun damaged areas of head and neck in elderly, presents as dome shaped or ulcerated nodule, tumor cells abut epidermis without a grenz zone (defined as relatively normal collagen forming a boundary between normal epidermis and a dermal lesion), also marked actinic elastosis, no classic features of fibrous histiocytoma

● Pleomorphic sarcoma - infiltrative, marked atypia, brisk mitotic activity, necrosis; no classic features of fibrous histiocytoma

● Pleomorphic fibroma - hypocellular, no epidermal hyperplasia, no classic features of fibrous histiocytoma

 

 

End of Skin / Soft Tissue Tumors > Atypical fibrous histiocytoma

 

 

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