Rosette-forming glioneuronal tumour of the 4th ventricle in a NF1 patient.

of the 4th ventricle in a 41 year-old man with neurofibromatosis type 1 (NF1). This patient had a family history of NF1 and presented with café-au-lait spots and multiple neurofibromata. At the age of 16 years (1983), he presented with severe headache and the head computed tomogram (CT) scan showed a 4th ventricular mass. The mass was partially resected and the histology was initially reported as a low grade astrocytoma. The patient died at age 41 years. The smear cytology from the original biopsy 25 years ago, showed a biphasic lesion composed of piloid cells with elongated fibrillary processes accompanied by Rosenthal fibers, and small round cells with finely granular nuclear chromatin forming rare neurocytic rosette (Figure 1a, b). The paraffin sections revealed a tumour with small round nuclei and scanty cytoplasm forming perivascular pseudorosettes surrounded by a low cellular glial component with piloid cells, microcystic areas and Rosenthal fibers. The perivascular cells were immunoreactive to synaptophysin, microtubule-associated protein 2 (MAP2) and neuron specific enolase (NSE) (Figure 1c-f) and immuno-negative for glial fibrillary acidic protein (GFAP). The glial areas were GFAP immuno-positive. There was no mitotic activity, vascular endothelial proliferation or tumour necrosis. At the follow-up after 23 years (2006), the patient had spastic gait and the MRI showed a 7 to 8 mm focus of increased signal in the fourth ventricular region within the periaqueductal grey matter of the right rostral pons (Figure 2a). It had no mass effect or enhancement. He suffered from schizophrenia and depression and two years later (2008), committed suicide. The general autopsy demonstrated findings of NF1 (multiple café-aulait spots and neurofibromata) and the brain was referred for neuropathological examination. Neuropathological examination revealed the residual tumour at the rostral pons around the fourth ventricle. The glial component was predominant with numerous microcystic areas. A few microcysts contained clusters of cells with small round nuclei and visible nucleoli. Morphologically, these cells resembled the neurocytic component of the original biopsy, but the neuronal markers were immuno-negative. Although relatively well circumscribed, there were atypical glial cells in the pontine tegmentum (Figure 2b-d). In the frontal cortex and