Pineal parenchymal tumors--utility of immunohistochemical markers in prognostication.

Background and objective: The pineal parenchymal tumors are rare, comprising 15 - 30% of all tumors of pineal region. Their histological classification alone has been found to be inadequate for prognostication. Hence, we correlated their immunohistochemical profile with the prognosis. Methods: A retrospective analysis of 33 pineal parenchymal tumors treated from 1990 -2004 was performed. The histological features of the tumors were reviewed and immunohistochemical staining for neurofilament protein (NF), MIB-1, synaptophysin and GFAP were performed. Results were correlated with the patients' survival. Results: The study comprised 6 pineocytomas (PC), 17 pineoblastomas (PB) and 10 pineal parenchymal tumors with intermediate differentiation (PPT-ID) which included 3 mixed PC/PB. The histological diagnosis was obtained from microsurgical biopsy/decompression, stereotactic or endoscopic biopsy. Adjuvant therapy was advised based on histology. All pineocytomas stained positive for NF. Most pineoblastomas (13/16) failed to show any immunoreactivity with NF. The mean MIB-1 labeling index in pineocytomas, PPT of ID and pineoblastomas were 1.58, 16.1 and 23.52 respectively (p < 0.001). All the tumors stained positive for synaptophysin, although the intensity of the staining varied. NF-positive tumors had a higher chance of disease-free state, irrespective of histological subgroup (p = 0.0036). The median disease-free survival in pineoblastomas with negative NF staining was 5 months, which was less than that of pineoblastomas with positive NF staining (32 months). Conclusions: Neurofilament immunoreactivity indicates better prognosis in pineal parenchymal tumors. The MIB-1 labeling index can be utilized as an additional tool to differentiate pineal parenchymal tumors into various subgroups.