The spectrum of morphological findings in pediatric central nervous system MN1-fusion-positive neuroepithelial tumors.

PURPOSE: Central nervous system high-grade neuroepithelial tumor with MN1 alteration (CNS-HGNET-MN1) is a rare entity defined by its DNA methylation pattern and pathologically considered to be high-grade with mixed patterns, stromal hyalinization, and with astrocytic differentiation. Our aim was to present six pediatric cases to contribute to the characterization of this group of tumors. MATERIAL AND METHODS: Six female patients aged 4 to 12 years with CNS tumors with MN1 alteration identified using genome-wide methylation arrays and/or RT-PCR were included. Clinicopathological, morphological, immunohistochemical, and molecular findings were analyzed. RESULTS: Tumor location was the parietal lobe in four and the intramedullary spinal cord in two. Two were morphologically diagnosed as ependymomas, one as gliofibroma, one as a HGNET-MN1 altered and the other two were difficult to classify. All were well-defined tumors, with a cystic component in three. Only two tumors had extensive stromal hyalinization, three had pseudopapillary formations, and four had other patterns. Multinucleated, clear, and rhabdoid cells were present. Necrosis and histiocyte clusters were also observed. Proliferative index was >10 in four. GFAP, EMA, CK, and SYN were variable, while Olig2 staining was mostly positive. Four of six patients with supratentorial tumors and complete resections were alive and tumor free after 2 to 10 years of follow-up. The two cases with medullary involvement and incomplete resections were alive and undergoing treatment 2 years after surgery. CONCLUSION: Neuroepithelial-MN1 tumors are challenging and suspicion requires molecular confirmation. Our pediatric data contribute to the knowledge for accurate diagnosis. Although further studies with a larger number of cases should be conducted in order to draw more robust conclusions regarding clinico-pathological features, here we present valuable pediatric data to increase the knowledge that may lead to the accurate management of this group of tumors.

Treatment response of CNS high-grade neuroepithelial tumors with MN1 alteration.

Central nervous system high-grade neuroepithelial tumor with MN1 alteration (CNS HGNET-MN1) is a rare recently described entity. Fourteen CNS HGNET-MN1 patients were identified using genome-wide methylation arrays/RT-PCR across seven institutions. All patients had surgery (gross total resection: 10; subtotal resection: four) as initial management followed by observation alone in three patients, followed by radiotherapy in eight patients (focal: five; craniospinal: two; CyberKnife: one) and systemic chemotherapy in three patients. Seven patients relapsed; five local and two metastatic, despite adjuvant radiotherapy, of which three died. Treatment of CNS HGNET-MN1 remains a major treatment challenge despite aggressive surgical resections and upfront radiotherapy, warranting new approaches to this rare malignancy.

Astroblastoma de bajo grado en lóbulo temporal / Astroblastoma of low grade in temporal lobe

Antecedentes: El astroblastoma es uno de los tumores más inusuales del sistema nervioso central, cuya histogénesis no ha sido determinada. Ocurre principalmente en niños y adultos jóvenes, pero se ha descrito casos congénitos y en adultos mayores. En general predomina en mujeres, con una relación de 2:1. Son de localización supratentorial en el 91% de los casos. El cuadro clínico depende de la localización, pero generalmente se presentan con cefalea, déficit neurológico, aumento de la presión intracraneal, náuseas, vómitos, alteraciones visuales y convulsiones. Macroscópicamente es una lesión bien delimitada e histológicamente muestra,las características pseudorosetas perivasculares con hialinización vascular frecuente y positividad variable para la proteína fibrilarglial ácida, proteína S100, vimentina y positividad focal para el antígeno epitelial de membrana. Presentación de caso:masculino de 37 años, con cefalea y crisis convulsiva parcial, y en quien los estudios de imagen por resonancia magnética evidenciaron una lesión quística en el lóbulo temporal izquierdo, con los hallazgos histológicos característicos de astroblastoma.Conclusión: Los astroblastomas son neoplasias raras, generalmente bien circunscritos y no infiltrativos, cuyo pronóstico depende del grado histológicoy la resección completa del tumor...