[Cell proliferation and cell death (apoptosis) as indices differentiating malignant from benign gastrointestinal...

We examined whether the determination of cell proliferation and cell death rates was useful in the differential diagnosis between benign and malignant myogenic tumors of gastrointestinal tract. As markers for cell proliferation and cell death, Ki-67 (MIB-1) positive rates or argyrophilic nucleolar organizer region (AgNOR) counts and apoptotic cell counts were determined in a total of 53 myogenic tumors comprising 36 leiomyomas and 17 leiomyosarcomas. Apoptotic cells were detected with the in situ nick end labeling method reported by Gavrieli in 1992 with modifications. Significant differences were observed in the Ki-67 positive rates (leiomyoma 1.8 +/- 1.4%, leiomyosarcoma 8.6 +/- 6.0%, p < 0.0001), in the mean AgNOR counts (leiomyoma 1.77 +/- 0.53, leiomyosarcomas 3.14 +/- 1.02, p < 0.0001), and in the apoptotic cell counts (median; leiomyoma 3.2, leiomyosarcoma 32.5 per 10(6) tumor cells, p < 0.005). All high grade sarcomas were picked up by the Ki-67 index of more than 7%, and almost all leiomyomas were thrown away by the AgNOR counts more than 3.0 within the low Ki-67 cases, which showed 81% of sensitivity and 97% of specificity. These results show that a combination use of Ki-67 and AgNOR is of use in the differential diagnosis between leiomyoma and leiomyosarcoma. Although a significant difference was also noted in apoptotic cell counts between these two categories, this seems not to be a practical index for the discrimination because apoptotic cell death is a rare event in gastrointestinal myogenic tumors.