H-, K-, and N-ras gene mutation in atypical fibroxanthoma and malignant fibrous histiocytoma

Atypical fibroxanthoma (AFX) which is histologically similar to malignant f ibrous histiocytoma (MFH), occurs in the sun-exposed skin. The presence of mutations at codons 12 and 13 of the H- and K-ras genes and in exons 1 and 2, which include codons 12, 13, and 61, of the N-ras gene was studied in 8 cases of AFX and 8 cases of storiform-pleomorphic-type MFH using polymerase chain reaction (PCR)-restriction fragment length polymorphism and PCR-sing le-conformation polymorphism. Two of the 8 cases of NIM showed ras mutation s in the H-ras gene at codon 12 (GGC-AGC) and in the K-ras gene at codon 13 (GGC-GAC). H- and K-ras gene mutations were not seen in any of the cases o f AIX (0 of 8). N-ras gene mutation was not detected in either the AFX (0 o f 8) or MFH (0 of 8) cases. In conclusion, although the number of cases in this study was small, H-and K-ras genes were present in some of the MFH cas es and accordingly may play an important role in the pathogenesis of MFH. I n addition, the finding that H-, K-, and N-ras gene mutations are not prese nt in AIX may indicate why AFX has a more favorable behavior than MFH. HUM PATHOL 32:1225-1231. Copyright (C) 2001 by W.B. Saunders Company.