Aggressive Vestibular Schwannomas Showing Rapid Growth after Surgical Resection; Clinicopathological Analysis of 15 Cases

ABSTRACT

OBJECTIVE: Vestibular schwannomas(VS) are known to be relatively slow growing tumors. Some VS, however, rapidly regrow or recur after surgical resection. Our objective is to investigate clinicopathological characteristics of these tumors and to elucidate factors, which can predict a rapid regrowth or recurrence after surgical resection. METHODS: Twenty-nine patients with VS underwent reoperation for regrowth or recurrence at the Department of Neurosurgery in Seoul National University Hospital between 1978 and 2000. Among these, 15 VS regrew or recurred rapidly(annual growth rate larger than 15mm/year). To compare morphology and proliferative activity, 15 cases of VS were randomly selected among consecutive operative cases between 1991 and 1999 with tumor size more than 4cm. As pathological parameters, cellularity, pleomorphism, mitosis, necrosis, invasion to adjacent tissue, and microvascular proliferation were examined. Proliferative indices(Ki-67 index) were also evaluated. Statistical analysis was performed using Fischers exact test and ANOVA test. RESULTS: The mean ages at a diagnosis were respectively 40.6(range 21-63), and 49.7(range 35-67) [p=0.438]. Male to female ratio was respectively 77, and 510[p=0.462]. In radiological findings, aggressive group at initial presentation had more lobulating contour than CG(7/13 cases vs 3/15 cases, p=0.001). In pathologic findings, cellularity and pleomorphism were significantly higher than those of control group(p=0.001). Proliferative index(Ki-67 index) was higher in aggressive group than control group [2.28(range 0.1-8.6) vs 0.59(range 0-1.5), p=0.034]. CONCLUSION: Vestibular schwannoma presented with lobulating contour, high proliferative index(Ki-67 index), and high cellularity or pleomorphism should be frequently investigated radiologically during follow-up for early detection of regrowth or recurrence.