[Significance of differential nuclear expression of Ki-67 in adult soft tissue sarcomas]

As many other nuclear markers, e.g. steroid receptors, Ki-67 epitopes are differentially expressed in tumour cell nuclei. It is unclear whether this phenomenon represents tumour cell heterogeneity, different stages of the cell-cycle or a biological phenomenon with prognostic impact. We analysed 104 primary adult soft tissue sarcomas (ASTS), formalin-fixed, paraffin-embedded, by APAAP and LSAB immunohistochemistry, epitope retrieval technique and 2 anti-Ki-67 antibodies (MIB-1 and Ki-S-5). Expression was evaluated by 4 indexes/1000 tumour cells: a) A-index: sum of all (weak, moderate and strong stained) Ki-67-nuclei, b) the weighed R-index: sum of all strong stained Ki-67+ nuclei x3, moderate stained nuclei x2 and weak stained nuclei x1, c) ID1-index: sum of all strong stained Ki-67+ nuclei, and d) ID2-index: sum of all strong and moderate stained Ki-67+ nuclei. Prognostic impact was analysed by Kaplan-Meier and logrank statistics with respect to overall survival. Quantitative Ki-67 expression did not vary significantly if determined by MIB-1 or Ki-S-5. The A-index turned out to be the strongest prognostic parameter within the whole group of ASTS as well as within each single sarcoma type investigated. Significant (p < 0.05) correlations between A-index and overall survival existed in LMS, LPS, MFH, SS, while a trend to significance (p = 0.06) was observed in MPNST. Quantitative evaluation of all three differential expression levels is necessary to obtain the most comprehensive prognostic informations of proliferation markers in ASTS.