Central neurocytoma

BACKGROUND Although central neurocytomas are considered benign, recent reports suggest that some patients with histologic atypia and/or elevated proliferation potential may have a poor outcome. METHODS A retrospective review identified 15 cases of central neurocytoma. Clinical follow‐up was available for 14 patients. Each tumor was evaluated for the presence of atypical histologic features, including cellular pleomorphism, endothelial proliferation, and necrosis. The proliferation potential was assessed by MIB‐1 immunohistochemistry. The correlation among histology, MIB‐1 labeling index (MIB‐1 LI), and clinical outcome was evaluated. RESULTS Histologic atypia was identified in 3 tumors (20%). The MIB‐1 LI ranged from 0.1% to 6.0 %, and 5 cases (33%) had an MIB‐1 LI >2%. The correlation between histologic atypia and MIB‐1 LI was poor, with only 1 tumor having both atypia and MIB‐1 LI >2%. Clinical follow‐up ranged from 13 to 255 months postoperatively (mean, 68 months). Although most patients were alive and well at last follow‐up, three developed symptomatic recurrence and one died as a result of increased tumor growth. The tumors from all 4 patients with a poor outcome had MIB‐1 LI >2%, but only 1 had histologic atypia. CONCLUSIONS The proliferation potential of central neurocytoma is a useful predictor of clinical outcome, whereas histologic atypia alone is not prognostically significant. It would be appropriate to recognize a subgroup of central neurocytomas with elevated proliferation potential as WHO Grade 2 lesions. The terms “atypical” and “anaplastic” are not appropriate to describe these lesions, as they imply a certain histologic appearance. The most accurate designation would be “proliferating neurocytoma.” Cancer 1999;85:1606–10. © 1999 American Cancer Society.