Clinicopathologic study of forty-four histologically pure supratentorial oligodendrogliomas

Few studies in recent years have specifically focused on pure oligodendroglial neoplasms. We retrospectively reviewed the clinicopathologic features of 44 patients with supratentorial oligodendroglioma diagnosed over a 19-year period (1974 to 1993). The study group consisted of 44 patients (age range, 8 to 69 years; median, 42 years), including 31 males. Thirty-one initially resected tumors (70%) were low grade and 13 (30%) were high grade (anaplastic). Using the St Anne-Mayo criteria for astrocytic tumors, 19 tumors (43%) were grade 2, 17 (39%) were grade 3, and 8 were (18%) grade 4. Histologic features of the tumors at initial resection included prominent nucleoli (N = 18, 41%), vascular proliferation (N = 9, 20%), necrosis (N = 6, 14%), and microcystic degeneration (N = 23, 52%). Nuclear atypia was graded as mild in 22 tumors (50%), moderate in 18 (41%), and marked in four (9%). The highest mitosis counts ranged from 0 to 10 mitotic figures (MF)/10 high-power fields (HPF) (mean, 2.4). Twelve patients (27%) had four or more MF/10 HPF. Initial surgery included gross total resection in 10 patients, subtotal resection in 16 patients, and biopsy in 14 patients. Thirty-one patients received adjuvant radiotherapy and 15 received chemotherapy. MIB-1 labeling indices ranged from 0 to 42.3 (median, 1.2 [low grade tumor median, 0.5; anaplastic tumor median, 6.2]). p53 immunostaining was observed in 18 of 43 stained tumors (41%). Overall, 5- and 10-year survival rates were 71% and 63%, respectively. The entire group had a median follow-up of 5.2 years. Age greater than 45 years (P = .02), mitosis counts of > or =4 MF/10 HPF (P = .0004), and MIB-1 labeling indices <2 (P = .03) were independent predictors of survival (Kaplan-Meier analysis). MIB-1 labeling indices <2 (P = .0009) was an independent predictor of disease-free survival. Low cell density (P = .04) and low histologic grade (P = .03) show trends with regard to being associated with longer survival. In conclusion, older patients (>45 years) or patients with tumors with an increased rate of cell proliferation generally have a worse prognosis. Although tumors of high histologic grade generally have a worse survival, the correlation was not statistically significant.