Pineal parenchymal tumour of intermediate differentiation

Background Pineal parenchymal tumours of intermediate differentiation (PPTID) were first described 20 years ago. We present a case of grade III PPTID. Clinical presentation An 8-year-old boy presented with 5 weeks of bifrontal headache, dipolopia, torticollis and gross bilateral papilledema. MRI showed a 16×10×12 mm pineal mass with a cystic and solid component, causing obstructive hydrocephalus. Clinical management consisted of posterior fossa craniotomy and resection. Results The tumour comprised diffuse sheets of undifferentiated small cells with hyperchromatic nuclei, small nucleoli and fine chromatin. Mitotic figures were inconspicuous, there was no necrosis or vascular endothelial proliferation and no markedly enlarged or atypical cells. Immunohistochemical staining showed expression of synaptophy-sin and retention of INI-1 staining. Neurofilament protein, GFAP, desmin, SMA, CD45, cytokeratin AE1/AE3 and EMA were negative. Ki-67 index was approximately 15-20%. The tumour was cellular, had relatively uniform nuclei, only one mitosis /10 HPF and a Ki-67 labelling index of approximately 15-20%. On this basis a diagnosis of PPTID (WHO grade III) was favoured over pineoblastoma (WHO grade IV). Conclusions Distinction between PPTID and pineoblastoma is difficult as it relies on arbitrary cut-off points in assessment of cellularity, mitotic activity and nuclear atypia. However, attempts should be made at a distinction, as this does seem to provide useful prognostic information.