Atypical fibroxanthoma and malignant fibrous histiocytoma

Atypical fibroxanthoma (AFX) and malignant fibrous histiocytoma (MFH) are soft-tissue tumours with variable aggressiveness. There is considerable debate about the relationship between these lesions, as histological and immunochemical differentiation is difficult.

Current opinions and evidence for diagnostic differences between AFX and MFH were reviewed. Consecutive cases of AFX and MFH were identified from our non-melanoma skin cancer (NMSC) database 1996-2007 for the Central Region of New Zealand.

Of the 50,411 NMSC lesions excised surgically from 26,138 patients, there were 101 AFX and 15 MFH cases. Three MFH cases were originally diagnosed as AFX. AFX and MFH share similar patient demographics, size and location and histological and immunohistochemical features. Most diagnostic biopsies of AFX were not followed by formal excision. Incomplete excision occurred in a large proportion of patients with AFX, which often did not proceed to re-excision, resulting in local recurrence. Cases of MFH generally underwent definitive treatment including re-excision if incompletely excised, and postoperative adjuvant radiotherapy.

The failure to treat AFX adequately may have resulted from the lack of appreciation of its aggressiveness. Contrary to the literature, we found few clinical differences between AFX and MFH. AFX and MFH also share similar histologic features and there are no immunohistochemical markers that reliably distinguish them. AFX is best considered a distinct entity with MFH, now reclassified as an undifferentiated pleomorphic sarcoma.