Surgical Pathology Criteria

Atypical Fibroxanthoma

Differential Diagnosis

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

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