Apoptosis in atypical fibroxanthoma and pleomorphic malignant fibrous histiocytoma.

Explanations for the disparate behavior of atypical fibroxanthoma (AFX) as compared with pleomorphic malignant fibrous histiocytoma (MFH) have included the proposition that the former is a pseudosarcoma. Nonetheless, these tumors are now widely regarded as the same process, but with AFX behaving benignly by virtue of its superficial location. However, a neoplasm's metastastatic potential has been proposed to be related to apoptosis. Therefore, the aim of the present study was to examine apoptotic counts, in conjunction with two important regulators of apoptosis: p53 and bcl-2, to determine if a distinction exists that may account for the different outcomes of these lesions. There was no significant statistical difference between eight AFX and nine pleomorphic MFH in terms of apoptotic behavior, proliferative indexes, p53 protein expression, or presence of bcl-2 product. Therefore, our results further support the contention that AFX should be regarded as a form of pleomorphic MFH, which demonstrates low malignant potential by virtue of its location in readily accessible sites.