Atypical fibrous histiocytoma and atypical fibroxanthoma: presentation of two cases.

We report two rare examples of dermal fibrohistiocytic stromal tumors: one case of atypical fibrous histiocytoma (AFH) and another one of atypical fibroxanthoma (AFX), which can be confused in surgical pathology diagnosis with high-grade malignant neoplasm. Histologically, a proliferation of mononuclear, spindle-shaped, or histiocytoid cells and/or multinucleated cells, usually admixed with inflammatory cells was observed in both cases, but some clinicopathological differences allowed their distinction. Immunohistochemistry is of a little help in differential diagnosis between these two entities however, it is very useful in differentiating with other groups of tumors. Recognition of AFH and AFX is important, especially to prevent incorrect aggressive treatment in those cases that may be confused with high-grade sarcoma. Because of the potentially aggressive behavior in rare cases and the lack of clear-cut predictive morphologic patterns that would specify a poor clinical outcome, complete surgical excision in all cases is recommended.