Atypical fibroxanthoma with osteoclast-like giant cells.

Atypical fibroxanthoma has a wide spectrum of histological appearances. A variant recently described is atypical fibroxanthoma with osteoclast-like giant cells. One case of this rare tumour is described. The tumour arose on the forehead of an 87-year-old woman in the form of a subepidermal nodule. The lesion was incompletely excised and recurred 6 months later without showing any characteristics of aggression. Six months after the second operation the patient was well and showed no signs of tumour recurrence. Immunohistological findings showed a "fibrohistiocytic" profile and were similar to those observed in other lesions rich in osteoclast-like giant cells. Flow cytometry revealed the diploid nature of the primary and the recurrent tumour. Atypical fibroxanthoma with osteoclast-like giant cells is a new variant of atypical fibroxanthoma that must be recognized by pathologists, since it can be confused with other benign and malignant tumours with a high proportion of multinucleate osteoclast-like giant cells.