MDM2 amplification, P53 mutation, and accumulation of the P53 gene product in malignant fibrous histiocytoma.

Fifty-two cases of malignant fibrous histiocytoma (MFH) were evaluated for amplification of the MDM2 gene, mutation of the P53 gene, accumulation of the P53 gene product, and their relation to disease-free and overall survival. All tests were carried out on formalin-fixed, paraffin-embedded tissue samples. Amplification of the MDM2 gene was detected in 15 of 52 cases (29%). Six of 52 cases (12%) demonstrated abnormalities of the P53 gene. Sequence analysis detected point mutations in four cases and a 1-base pair deletion in one case, whereas differential polymerase chain reaction (dPCR) indicated that the P53 gene had been entirely deleted in one case. Eight of 52 cases (15%) demonstrated staining for the P53 protein in >10% of tumor cells. The presence of MDM2 amplification did not have a significant effect on either disease-free or overall survival. Patients with accumulation of the P53 gene product did not differ in disease-free or overall survival from patients without P53 accumulation. Survival also was not significantly different in patients with genetic aberration in P53. However, when the patients were stratified by histologic grade, the results indicated that patients with alterations in the P53 gene may have shorter overall survival.