atypical fibroxanthoma atypical fibroxanthoma atypical fibroxanthoma of the skin is a low-grade malignancy related to malignant fibrous histiocytoma, which it resembles histologically.: 613 atypical fibroxanthomaspecialtyoncology, rheumatology diagnosis differential diagnoses squamous cell carcinoma malignant fibrous histiocytoma treatment surgical excision with clear margins. epidemiology it occurs most commonly on the skin of sun-exposed, elderly patients. the majority of tumours are on the scalp, face, ears and upper limbs, but less commonly the tumour occurs on the limbs and trunk when there is a lack of association with sun exposure in younger individuals. the condition has also been noted in organ transplant recipients who may be in a state of immunosuppression. it has been reported that there is a predominance in men (70% men versus 30% women).