Clinicopathologic growth factors of acoustic neuromas.

BACKGROUND Understanding the tumor growth rate is very important when considering strategies for the treatment of an acoustic neuroma, although the natural course of acoustic neuromas has not been reviewed in detail. METHODS The clinicopathologic features and the postoperative growth of tumors were evaluated in 32 patients with acoustic neuromas. This study was undertaken to assess the variability of the growth potential of cells within an acoustic tumor and to determine the relationships between the growth rate and the clinicopathologic characteristics of the patients with acoustic neuromas, including age at surgery, gender, tumor location and preoperative size, the duration of the symptoms, the presence of cystic regions, the presence of Antoni type A and B cells, the tumor cell density, tumor vascularity, mitotic rate, the presence of hyaline degeneration and hemosiderin deposition, nucleolar organizer regions (NORs), and the level of proliferating cell nuclear antigen (PCNA). RESULTS The growth patterns of the tumors were divided into three groups according to their growth rate: a regression group, a "no-growth" group (growth rates from 0-0.11 cm/year) and a progression group (growth rates from 0.19-1.72 cm/year). An additional operation was required in all patients whose growth rate was more than 0.38 cm/year. A statistical study on the factors associated with an increased growth rate showed that the three histopathologic factors most significantly associated with a postoperative growth rate were hyaline degeneration (p < 0.05), cell density (p < 0.005), and PCNA labeling index (p < 0.005). CONCLUSIONS These results strongly suggest that acoustic tumors can be subdivided into several groups, based upon different biologic activities and tumor growth rates.