Association of proliferative activity and size in acoustic neuroma: implications for timing of surgery

Object. Acoustic neuroma is the most frequent benign tumor of the cerebellopontine angle, and surgery is still the most common form of treatment. To gain better insight into the dysregulated mechanisms causing growth of acoustic neuroma, the authors studied the proliferative activity of 34 consecutive samples by analyzing immunohistochemical staining with Ki-67 and proliferating cell nuclear antigen (PCNA), and apoptosis based on the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling. Data from these analyses were correlated with clinical parameters (that is, tumor size, duration of symptoms, and patient age). Methods. Apoptotic cells were found in none of the tumors. Proliferation measured on staining with Ki-67 and PCNA correlated with tumor size, but not with patient age or duration of symptoms. The authors demonstrated that tumors 18 mm or smaller in diameter have lower proliferation indices and growth rates, compared with tumors larger than 18 mm with high proliferative indices and growth rates. Additionally, they observed that these more aggressive, larger tumors occur mostly in patients younger than 50 years of age. Conclusions. Patients with tumors larger than 18 mm in diameter and who are younger than 50 years of age sustain an enhanced risk for fast-growing tumors because of these lesions' enhanced proliferative activity. For these patients the authors recommend active therapy.