GROWTH OF VESTIBULAR SCHWANNOMAS - IN-SITU MODEL EMPLOYING THE MONOCLONAL-ANTIBODY KI-67 AND DNA FLOW-CYTOMETRY

Vestibular schwannoma (VS) growth potentials were studied in an in sit u model, in which the cycling cellular fraction was determined immunoh istochemically by applying the mouse monoclonal Ki-67 antibody, and th e tumor ploidy was estimated by DNA flow cytometry in a consecutive se ries of 124 VSs. The tumors were classified according to the average n umber of positively stained nuclei in 10 high-power fields into three groups: 28 highly (>10), 33 moderately (>5-10) and 63 low proliferatin g (less than or equal to 5). The intratumoral proliferative variation was studied in 10 tumors. Only slight variation in the number of the p ositively stained nuclei were observed. Six of seven tumors removed be cause of macroscopically documented growth by computed tomography (CAT ) scan were moderately or highly proliferative. Proliferation of VS wa s correlated to prospectively registered clinical data. A statisticall y significant relation was found between VS proliferation and the pred iagnostic duration of symptoms (p = 0.0001). The proliferative status was unrelated to age, sex, and tumor size. Flow-cytometric determinati on of DNA index of the 124 tumors revealed 12 tetraploid (DNA index = 2), 110 diploid (DNA index = 1) and two nondiploid tumors. A statistic ally significant relation was noted between tumor ploidy and prolifera tion status expressed by Ki-67 (p = 0.024). The tetraploid tumors show ed significantly lower proliferation compared with the diploid tumors. Tumor ploidy was statistically unrelated to age, sex, tumor size, and duration of symptoms. The results of this study provide a link betwee n the immunohistochemical, flow cytometric findings, and clinical data , which could probably be relevant in identifying patients at risk for rapid tumor growth and tumor recurrences, because a rapid test for ce ll proliferation is now available.