OBJECTIVETo investigate the clinicopathologic features and 19q13.42 gene changes in embryonal tumors with multilayered rosettes (ETMR).

METHODSImmunohistochemistry and fluorescence in situ hybridization (FISH) were performed in three ETMRs.

RESULTSThe 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.

CONCLUSIONSETMR 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.