The patient went on to have an endoscopic biopsy and thrid ventriculostomy.

Histology

Sections show fragments of a cellular tumor. The tumor forms sheets of cells, with only the occasional small rosette seen. The tumor cells are monomorphic, with round-to-oval nuclei, fine stippled chromatin, and eosinophilic-to-pale cytoplasm. There are between 1 and 2 mitoses per 10 high power fields. There is no necrosis and no nuclear atypia. There are plentiful calcifications.

IMMUNOHISTOCHEMISTRY: The tumor cells are diffusely and strongly positive with synaptophysin. Occasional scattered cells are positive with NFP. The Topoisomerase proliferation index is approximately 6-7%.

FINAL DIAGNOSIS: Pineal parenchymal tumor of intermediate differentiation (PPTID) (WHO Grade III)