Contributed by George A. Alexiou1 MD, PhD, Kalliopi Stefanaki2 MD, PhD, Maria Moschovi3 MD, PhD, George Sfakianos 1 MD, PhD, Neofytos Prodromou 1 MD, PhD.
1Department of Neurosurgery, 2Department of Pathology, 3Department of Hematology-Oncology, Children's Hospital ''Agia Sofia'', Athens, Greece.
A 2-year-old boy presented with gait imbalance and strabismus over the last two weeks. Five days before admission he began to vomit and became irritable. On admission a brain computed tomography was performed and revealed a large midline posterior fossa mass; the lesion was heterogeneous, cystic partly solid with calcifications (Figure 1). Magnetic resonance imaging that ensued demonstrated a 5x4.9x4.7cm mass within the 4th ventricle, extending through foramen of Luschka into the left cerebello-pontine angle without infiltration of the vermis (Figure 2). The lesion showed heterogenous enhancement after contrast administration (Figure 3). The patient was operated upon and a gross total resection of the mass was performed.
GROSS AND MICROSCOPIC PATHOLOGY
Macroscopically there was a friable gray-white tissue with foci of hemorrhage and necrosis. Microscopically the tumor showed malignant areas with numerous mitoses and rare but distinct clusters of cells (Figure 4) while in other areas the tumor cells had more cytoplasm, mild nuclear atypia and fewer mitoses (Figures 5, 6, 7). Synaptophysin stained the cells in the highly mitotic malignant areas (Figure 8), but cells in the low mitotic area were stained with desmin (Figure 9), myogenin /Myf-4 (Figure 10) and MyoD1. There was no expression of keratin, EMA and GFAP. The Ki-67/MIB-1 proliferation index was detected in 30-40% of the nuclei of the cells in the malignant areas. P-53 protein was expressed in 20-30% of the nuclei, while bcl-2 protein was detected in 20% of the tumor cells. INI-1 nuclear expression was retained in all neoplastic cells (>95%).