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Skin / Soft Tissue Tumors
Atypical fibroxanthoma (AFX)
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 variant of MFH-pleomorphic with low grade behavior
Terminology
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● Also called intermediate fibrous histiocytoma
● Part of WHO classification for skin tumors, not soft tissue tumors
● See also Ear chapter
Epidemiology
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● Usually elderly; rarely in younger individuals
Clinical
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● Elderly - rapidly growing dome-shaped or polypoid nodule, often ulcerated, in head and neck due to sun damage or radiation therapy (eMedicine)
● Younger individuals - rare; large mass in limb or trunk
● May clinically resemble carcinoma
Case reports
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● 63 year old man with metastatic tumor from eyebrow area to face (Archives 2006;130:735)
● 81 year old woman with lower leg lesion (Dermatology Online Journal 14(1))
● 81 year old man with widespread peritoneal metastases (AJSP 2006;30:1041)
Treatment and prognosis
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● Local excision; Mohs micrographic surgery may be most effective (Dermatol Surg 2009;35:765)
● Rarely recurs or metastasizes
● Poor prognostic indicators are history of immunosuppression, recurrence
Gross description
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● Polypoid, ulcerated, usually small
Gross images
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Irregular polypoid tumor 66 year old man with scalp lesion
Other images: elevated, red, ulcerated lesion
Micro description
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● Bizarre tumor cells in hypercellular, spindly stroma with frequent mitotic figures, many atypical
● Also smaller fibroblastic, myofibroblastic and histiocyte-like cells with pleomorphism and angulated nuclei
● Histologically identical to MFH-pleomorphic but centered in dermis
● Tumor cells push aside surrounding pilosebaceous units and eccrine glands
● Background stroma appears inflammatory or reactive
● Typically does not involve epidermis or subcutaneous tissue; no grenz zone
● Lacks classic features of fibrous histiocytoma (entrapped hyalinized collagen bundles and epidermal hyperplasia)
● No necrosis, no vascular invasion, no infiltrative margins
● Variants include chondroid, clear cell (J Cutan Pathol 2006;33:343), granular cell (Am J Dermatopathol 2007;29:84), keloidal (J Cutan Pathol. 2009;36:535), myxoid (J Cutan Pathol 2009 Mar 3 [Epub ahead of print]), osteoclastic, osteoid, pigmented (Actas Dermosifiliogr 2009;100:321), spindle cell
Micro images
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Exophytic cellular and ulcerated nodule Fascicles of atypical spindle cells
Tumor is limited to dermis but Marked cellularity
otherwise resembles MFH-pleomorphic and pleomorphism
with marked cellularity, pleomorphism,
mitotic figures and clumped chromatin
Bizarre cells are characteristic Spindled variant has less pleomorphism
81 year old woman with Highly anaplastic cells and
lower leg lesion inflammatory cells
Factor XIIIa p53
Other images: spindle and epithelioid cells with atypia; ulcerated tumor #1; #2; #3; #4; #5; nodular spindle cell tumor #1; #2
● Figure 1: eyebrow primary, figures 2-4: facial metastasis (fig 4 is CD68)
Positive stains
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● Vimentin, CD68, alpha-1-antitrypsin, alpha-1-antichymotrypsin
● CD117 (Am J Dermatopathol 2008;30:34), CD99 (73%, AJCP 2002;117:126), CD10 (Australas J Dermatol 2005;46:235)
● Factor XIIIa (focal), calponin (30%, Virchows Arch 2002;440:404), desmin (30%), smooth muscle actin (30%)
Negative stains
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● Keratin, EMA, S100 (although S100+ Langerhans cells may be present)
● HMB45 (rarely positive, J Cutan Pathol 2004;31:284), caldesmon, p63
Electron microscopy (ultrastructure)
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● Myofibroblasts, fibroblasts and primitive mesenchymal cells
Molecular
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● Diploid
Differential diagnosis
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● Must exclude tumors with AFX-like patterns, other lines of differentiation, significant involvement of subcutis, necrosis, vascular invasion or infiltrative margins
● Atypical fibrous histiocytoma - may not have central ulcer, has areas of classic fibrous histiocytoma
● Desmoplastic melanoma - may have focal AFX-type features and stain negative for melanocytic markers (Am J Dermatopathol 2007;29:551)
● Pleomorphic leiomyosarcoma
● Squamous cell carcinoma-spindle cell type (deep extension, p63+, J Cutan Pathol 2009;36:543)
Additional references
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End of Skin / Soft Tissue Tumors > Atypical fibroxanthoma
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