ABSTRACT
<p><b>OBJECTIVE</b>To investigate the clinicopathologic features and 19q13.42 gene changes in embryonal tumors with multilayered rosettes (ETMR).</p><p><b>METHODS</b>Immunohistochemistry and fluorescence in situ hybridization (FISH) were performed in three ETMRs.</p><p><b>RESULTS</b>The average age of the patients were 34 months. Imaging revealed huge masses with inhomogeneous enhancement and two cases showed cystic lesions. Follow-up data showed 14 and 38 months survival in two children, the third had a recurrence 4 months after operation. Morphologically, the tumor was mainly composed of dense small primitive neuroepithelial cells in patchy or multilayer rosettes within a background of advanced neuronal differentiation, containing neurocytes, ganglion cells, and neuropil-like background. Immunohistochemical staining showed the neuronal marker, synaptophysin, was positive in differentiated areas. Nestin as a neural stem cell marker was immunoreactive in the primitive neuroepithelial cells including multilayered rosettes. Neurons with positive expression of NeuN were observed occasionally. Ki-67 index was up to 40%-80% in the undifferentiated cells and rosettes, but was only 1%-3% in the differentiated areas. CD99 was positive in perivascular papillary pattern areas in one case. 19q13.42 amplification was detected in more than 30% of tumor cells in all cases.</p><p><b>CONCLUSIONS</b>ETMR is a unique entity with distinctive clinical and pathological features. Chromosome 19q13.42 abnormality is valuable for confirming the diagnosis and for further treatment research.</p>