PRIMARY MALIGNANT RHABDOID TUMORS OF THE CENTRAL-NERVOUS-SYSTEM - AN IMMUNOHISTOCHEMICAL AND ULTRASTRUCTURAL-STUDY

Three cases of primary rhabdoid tumour of the CNS (RT-CNS) are present ed. In case 1 a hemispheric tumour developed in a 10.5 months old girl , who survived for 6 months after incomplete resection, radio-and poly chemotherapy. Case 2 was a 4 years and 8 months old boy with a large I IIrd ventricle tumour, who died of leptomeningeal tumour dissemination 7 months after diagnosis despite radiotherapy. In case 3 a pineal mas s occurring in a 14 month old female was radioresistant and totally ex stirpated. The child died due to tumour recurrence two months later. A utopsy examination revealed widespread leptomeningeal dissemination. A ll three cases fulfilled light and electron microscopic criteria of RT -CNS including abundant eosinophilic cytoplasm, vesicular nuclei with large nucleoli and conspicuous anti-vimentin positive filaments. Exten sive immunohistochemical studies showed expression of epithelial (EMA, KL1), macrophage (alpha-1 antichymotrypsin), neuro-ectodermal (GFAP, NSE, beta-tubulin III) and myogenic markers (desmin, actin). Different stress proteins (alpha-B crystallin, HSP70) were also expressed. Tumo ur cells showed a proliferation (MIBI) index of 28.4% (case 1) and 33. 4% (case 2). From our study it can be concluded that RT-CNS reveals si gnificant immuno-morphological heterogeneity thus supporting the view that it is nor a specific pathological entity but merely a phenotypic appearance of different neoplasms, some of which are linked to primiti ve neuro-ectodermal tumours.