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Skin - Nonmelanocytic tumors

Other tumors of skin

Atypical fibroxanthoma (AFX)

Reviewers: Christopher Hale, M.D., Vijay Shankar, M.D. (see Reviewers page)
Revised: 26 October 2012, last major update August 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.


● Dermal variant of MFH-pleomorphic with low-grade behavior
● Also called intermediate fibrous histiocytoma
● Part of WHO classification for skin tumors, not soft tissue tumors

Clinical features

● Rapidly growing small dome-shaped or polypoid nodule on sun-damaged areas of head and neck of elderly (eMedicine-atypical fibroxanthoma)
● May present as bleeding ulcer < 2 cm
● Rarely presents as large mass in limb or trunk of younger individuals, or post radiation therapy
● May clinically resemble carcinoma
● Must exclude tumors with AFX-like patterns, other lines of differentiation, significant involvement of subcutis, necrosis, vascular invasion or infiltrative margins (Stanford Medicine)
● Poor prognostic indicators: history of immunosuppression, recurrence

Case reports

● 21 year old woman with nasal nodule (Can J Plast Surg 2007;15:169)
● 63 year old man with metastatic tumor from eyebrow area to face (Arch Pathol Lab Med 2006;130:735)
● 81 year old man with widespread peritoneal metastases (Am J Surg Pathol 2006;30:1041)
● 81 year old woman with lower leg lesion (Dermatol Online J 2008;14:1)


● Local excision; Mohs micrographic surgery may be effective (Dermatol Surg 2009;35:765)
● Rarely recurs or metastasizes

Clinical images

Irregular polypoid tumors

21 year old woman with nasal nodule

Solitary dome shaped nodule

Gross description

● Polypoid, ulcerated, usually small

Micro description

● Well circumscribed, appears symmetric at scanning magnification
● Bizarre multinucleated 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
● Background stroma appears inflammatory or reactive
● Pushes aside surrounding pilosebaceous units and eccrine glands
● Typically does not involve epidermis or subcutaneous tissue
● Lacks classic features of fibrous histiocytoma (entrapped hyalinized collagen bundles and epidermal hyperplasia)
● No grenz zone, no necrosis, no vascular invasion, no infiltrative margins

● Variants: angiomatoid, 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;36:1177), osteoclastic, osteoid, pigmented (Actas Dermosifiliogr 2009;100:321)

Micro images

Exophytic cellular nodule with ulceration

Fascicles of atypical spindle cells

Tumor is limited to dermis but otherwise resembles MFH-pleomorphic with marked cellularity,
prominent pleomorphism, mitotic figures and clumped chromatin

Marked cellularity and pleomorphism

Characteristic bizarre cells

Spindle variant has less pleomorphism

81 year old woman with lower leg lesion

Various images, contributed by Dr. Angel Fernandez-Florez, Hospital El Bierzo, Spain

Angiomatoid variant

Fig A: edge of lesion shows hyperchromatic cells next to elastotic dermis (arrow)
Fig B/C: atypical spindle cells and histiocytes, atypical mitotic figure (arrow)
Fig D: alpha-1-antichymotrypsin positive

Fig 1: eyebrow primary
Fig 2-4: facial metastasis (fig 4 is CD68)

Factor XIIIa


CD68, contributed by Dr. Angel Fernandez-Florez, Hospital El Bierzo, Spain

CD10, contributed by Dr. Angel Fernandez-Florez, Hospital El Bierzo, Spain

AE1-AE3, contributed by Dr. Angel Fernandez-Florez, Hospital El Bierzo, Spain

Spindle and epithelioid cells with atypia

Ulcerated tumor #1, #2, #3, #4

Nodular spindle cell tumor #1, #2

Positive stains

● Vimentin, CD68, alpha-1-antitrypsin, alpha-1-antichymotrypsin, Factor XIIIa (focal)
● CD117 (Am J Dermatopathol 2008;30:34), CD99 (73%, Am J Clin Pathol 2002;117:126), CD10 (Australas J Dermatol 2005;46:235)
● D2-40 (50%, J Cutan Pathol 2011;38:631), calponin (30%, Virchows Arch 2002;440:404), desmin (30%), smooth muscle actin (30%)
● Procollagen-1, CD31 (5%), p75 (J Cutan Pathol 2011;38:631)

Negative stains

● Keratin (J Cutan Pathol 2010;37:301), EMA, S100 (although S100+ Langerhans cells may be present)
● HMB45 (rarely positive, J Cutan Pathol 2004;31:284), caldesmon, desmin

Electron Microscopic

● Myofibroblasts, fibroblasts and primitive mesenchymal cells


● Diploid

Differential diagnosis

● Squamous cell carcinoma-spindle cell type: deep extension, p63+ (J Cutan Pathol 2009;36:543)
● Desmoplastic melanoma: may have focal AFX-type features and stain negative for melanocytic markers ( Am J Dermatopathol 2007;29:551)
● Atypical fibrous histiocytoma
● Angiosarcoma-spindle cell variant

End of Skin - Nonmelanocytic tumors > Other tumors of skin > Atypical fibroxanthoma (AFX)

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