Malignant peripheral nerve sheath tumours: high Ki67 labelling index is the significant prognostic indicator

Aims: We investigated p53, Ki67, MDM2, and p21(WAF1/CIP1) in order to evalu ate its relationship with prognosis in malignant peripheral nerve sheath tu mours (MPNST). Methods and results: In 49 cases of MPNSTs, the immunohistochemical studies of Ki67, p53, MDM2, p21(WAF1/CIP1) and polymerase chain reaction single-st rand conformation polymorphism (PCR-SSCP) with direct sequencing of p53 wer e performed with the formalin-fixed paraffin-embedded tissue. In 43 cases w ith survival data available, an evaluation of the prognostic significance o f clinicopathological factors was also carried out. A high Ki67 labelling i ndex (LI) (>25%) was correlated with a reduced survival rate in the 43 case s of MPNST (P = 0.0106, log-rank test). Furthermore, there was a significan t correlation between the Ki67 LI and the immunohistochemical expression of p53 or MDM2. In 17 MPNST cases, PCR amplification of exons 5 through 8 of the p53 gene was successful. One case showed a base change of codon 240 (AG T --> AGC), but translated amino acid (Ser) remained unchanged. Multivariat e Cox analysis of our series showed that the association of von Recklinghau sen's disease, tumour depth, and the presence of rhabdomyoblasts (malignant triton tumour) each had an independent negative impact on overall survival . Conclusion: High Ki67 LI (>25%) was of significant prognostic value in MPNS T.