HUMAN VESTIBULAR SCHWANNOMA GROWTH IN THE NUDE-MOUSE - EVALUATION OF A MODIFIED SUBCUTANEOUS IMPLANTATION MODEL

Hypothesis: Based on the hypothesis that vestibular schwannomas can be successfully implanted and grown in the nude mouse model, an in vivo experiment was designed for subcutaneous implantation of solid vestibu lar schwannoma tissue. Background: Vestibular schwannomas are benign t umors arising from Schwann cells of cranial nerve VIII. Little in vivo research has been carried out with these tumors, due in part to the d ifficulty to grow cells in culture or maintain tumor in an animal mode l. Recently, vestibular schwannomas have been implanted in nude mice w ith moderate success. The current study evaluates a modification of pr ior techniques in an effort to establish a dependable research model. Methods: Thirty-six nude mice were implanted with variable-sized vesti bular schwannoma tissue from three human subjects. Volumes implanted r anged from 14-170 mm(3). Mice were observed for 28 days and individual volumes recalculated. Eleven of the mice were observed for a total of 56 days with volumes re-evaluated, and tumors subsequently were remov ed for assessment of viability and vascularity. Results: At 28 days. 3 6 tumors(100%) showed take with 34 tumors (94%) showing macroscopic gr owth. The 11 tumors observed for 56 days showed a trend of stable or d ecreased size at 56 days compared with that of the 28-day measurement. Over-all growth from time of implantation to measurements at 56 days was noted in 8 (73%) of 11 tumors when measured at the skin and in 10 (91%) of II tumors when direct tumor volume was measured. One hundred percent of rumors evaluated microscopically at 56 days was viable. All tumors at the time of removal had significant vascularity with a mean of 70.68% (SD = 23.42) of surface covered with vessels. There were no significant differences ill take and growth for the larger tumor spec imens compared with those of smaller sizes. Conclusion: Human vestibul ar schwannomas successfully can be implanted and maintained in the sub cutaneous pocket of the nude mouse. This in vivo tumor model provides a reliable, accessible base for further research with vestibular schwa nnomas.