Atypical Fibroxanthoma
Differential Diagnosis
- Malignant fibrous histiocytoma
- Atypical fibrous histiocytoma / dermatofibroma with monster cells
- Pleomorphic fibroma
- 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 |
