Stanford School of Medicine
Surgical Pathology Criteria
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Atypical Fibroxanthoma


  • Cellular cutaneous mesenchymal neoplasm with at least focal pleomorphism and lacking evidence of epithelial or melanocytic differentiation

Alternate / Historical Names

  • AFX
  • Cutaneous pleomorphic undifferentiated sarcoma

Diagnostic Criteria

  • This is a diagnosis of exclusion and the following must be ruled out in every case:
    • Carcinoma
    • Melanoma
    • Smooth muscle tumor
    • Nerve sheath tumor
    • Pleomorphic malignant fibrous histiocytoma
  • Nearly always involves sun damaged skin of the elderly
    • May also occur in irradiated areas
  • Involves dermis
    • Usually abuts epidermis
    • May ulcerate
    • More than minimal extension into subcutaneous tissue is not allowed
  • Compressive margins
  • Vascular invasion not allowed
  • Cellular neoplasm composed of spindled to large pleomorphic cells
    • Most common pattern is identical to pleomorphic malignant fibrous histiocytoma
      • Numerous large polygonal cells
      • Large bizarre nuclei
      • Numerous atypical mitotic figures
    • Spindle cells may predominate
      • Pleomorphic cells should be present at least focally
    • Xanthoma cells frequently present
  • Occasional findings:
    • Hemosiderin
    • Osteoclast-like giant cells
    • Osteoid
    • Clear cytoplasm
      • Rarely predominates
      • Lipid positive, glycogen negative
    • Granular cytoplasm
      • Rarely predominates
  • Richard L Kempson MD
    Robert V Rouse MD
    Department of Pathology
    Stanford University School of Medicine
    Stanford CA 94305-5342

    Original posting: August 10, 2008
    Last update December 31, 2008


Supplemental studies


CD10 >95%
Procollagen 1 80-90%
CD99 73%
Keratin, including high molecular weight Negative
P63 Negative
S100 Negative
HMB45, MelanA Negative
Smooth muscle actin 40%
Desmin Rare
CD68 50%

Differential diagnosis

  • Carcinoma and melanoma must be ruled out by immunohistochemistry in every case
  • In situ squamous carcinoma and melanoma must be searched for in every case
Malignant Fibrous Histiocytoma Atypical Fibroxanthoma
Usually over 2 cm in size Usually under 2 cm in size
Involves subcutis, fascia or muscle At most, minimal involvement of subcutis; no involvement of fascia or muscle
Frequent necrosis Necrosis rare
May have vascular invasion No vascular invasion


Atypical Fibrous Histiocytoma / Dermatofibroma with Monster Cells Atypical Fibroxanthoma
More often on extremities and trunk Virtually restricted to head and neck
Grenz zone between lesion and epidermis Usually abuts epidermis, frequently ulcerated
Areas of typical fibrous histiocytoma with short intersecting bundles of small fibroblastic cells surrounding collagen fibers Lacks areas of typical fibrous histiocytoma
CD68 negative CD68 50%
May have necrosis Lacks necrosis
Mitotic figures rare Mitotic figures numerous, often atypical


Pleomorphic Fibroma Atypical Fibroxanthoma
Various sites, more often on extremities and trunk than head and neck Virtually restricted to head and neck
Paucicellular Cellular
Lacks xanthoma cells May have xanthoma cells
Mitotic figures rare but may be atypical Mitotic figures frequent, many of which are atypical


  • Nearly always involves sun damaged skin of the elderly
    • May also occur in irradiated areas
  • Recurrence rate 0-10%
  • When strictly defined, metastases virtually never occur
    • Metastatic cases are probably carcinoma, melanoma or MFH


  • Kempson RL, Fletcher CDM, Evans HL, Henrickson MR, Sibley RS. Tumors of the Soft Tissues, Atlas of Tumor Pathology, AFIP Third Series, Fascicle 30, 2001
  • Weiss SW, Goldblum JR. Enzinger and Weiss's Soft Tissue Tumors, 5th edition, 2008
  • Fretzin DF, Helwig EB. Atypical fibroxanthoma of the skin. A clinicopathologic study of 140 cases. Cancer. 1973 Jun;31(6):1541-52.
  • Mirza B, Weedon D. Atypical fibroxanthoma: a clinicopathological study of 89 cases. Australas J Dermatol. 2005 Nov;46(4):235-8.
  • Crowson AN, Carlson-Sweet K, Macinnis C, Taylor JR, Battaglia T, LaMar WL, Minor D, Sutter S, Hill T. Clear cell atypical fibroxanthoma:a clinicopathologic study. J Cutan Pathol. 2002 Jul;29(6):374-81.
  • Rudisaile SN, Hurt MA, Santa Cruz DJ. Granular cell atypical fibroxanthoma. J Cutan Pathol. 2005 Apr;32(4):314-7.
  • Longacre TA, Smoller BR, Rouse RV. Atypical fibroxanthoma. Multiple immunohistologic profiles. Am J Surg Pathol. 1993 Dec;17(12):1199-209.
  • Jensen K, Wilkinson B, Wines N, Kossard S. Procollagen 1 expression in atypical fibroxanthoma and other tumors. J Cutan Pathol. 2004 Jan;31(1):57-61.
  • Hultgren TL, DiMaio DJ. Immunohistochemical staining of CD10 in atypical fibroxanthomas. J Cutan Pathol. 2007 May;34(5):415-9.
  • de Feraudy S, Mar N, McCalmont TH. Evaluation of CD10 and procollagen 1 expression in atypical fibroxanthoma and dermatofibroma. Am J Surg Pathol. 2008 Aug;32(8):1111-22.
  • Monteagudo C, Calduch L, Navarro S, Joan-Figueroa A, Llombart-Bosch A. CD99 immunoreactivity in atypical fibroxanthoma: a common feature of diagnosticvalue. Am J Clin Pathol. 2002 Jan;117(1):126-31.
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