Twenty-seven cases of pineal parenchymal tumours of intermediate differentiation: mitotic count, Ki-67 labelling index and extent of resection predict prognosis.

OBJECTIVE: Optimal grading and treatment of pineal parenchymal tumours of intermediate differentiation (PPTID) have not been established due to their rarity. After careful review of more than 500 pineal region tumours treated in our centre, 27 patients with PPTID were identified.

METHODS: Diagnoses were confirmed according to WHO classification and graded as suggested by Jouvet et al. The relationship between the WHO grade, histopathological characters, management and outcome was analysed.

RESULTS: The WHO grade did not demonstrate significant correlation with outcome. Mitotic count and Ki-67 labelling index (LI) were detected as prognostic factors. Stratification of patients by mitotic count and Ki-67 LI correlated significantly with overall survival and progression-free survival. All the patients underwent resection. Gross total resection (GTR) was achieved in 16/27 (59.3%) patients, subtotal resection in 6/27 (22.2%) patients and partial resection in 5/27 (18.5%) patients. Log rank test confirmed GTR correlated with significantly better survival. Adjuvant therapy had a tendency to correlate significantly with progression-free survival. Among the high-risk patients, 6/9 patients with residual tumour received radiotherapy and 50% (3/6) were free of local tumour recurrence. In the other three high-risk patients with residual tumour who did not receive adjuvant therapy, recurrence occurred early and Ki-67 LI predicted prognosis.

CONCLUSIONS: Risk evaluation combining mitotic count and Ki-67 LI predicts prognosis. Surgery is the most efficient management. GTR is related to better prognosis. If GTR is not achieved, adjuvant therapy might delay tumour progression or recurrence, especially in high-risk patients.