Atypical fibroxanthoma with perineural or intraneural invasion: report of two cases.

We report two cases of atypical fibroxanthoma (AFX) that both had the previously unreported feature of neural invasion (one perineural and the other intraneural). AFXs recur in approximately 10% of cases but only rarely metastasize. Features associated with recurrence are inadequate excision and invasion into fat. Features associated with metastasis include recurrence, vascular invasion, deep tissue invasion, and tumor necrosis. Both of these tumors invaded deeply into subcutaneous fat and reached the deep fascia. Some authors would regard such cases as malignant fibrous histiocytoma (MFH) because of such deep extension; however, the concept of AFX as a superficial variant of MFH is outmoded--AFX is a distinct clinicopathologic entity with established clinical, histological, and immunohistochemical features.