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Embryonal tumor with multilayered rosettes (ETMR) is a rare and highly aggressive embryonal central nervous system tumor that primarily affects young children. It is characterized by (1) amplification of the C19MC miRNA cluster at 19q13.42 and (2) immunohistochemical tumor cell positivity for LIN28A. We describe the case of a 3-year-old girl who presented with a 2-week history of multiple neurological deficits. Based primarily on imaging findings that revealed a large pontine tumor, biopsy was not performed and the patient was clinically diagnosed with a “diffuse intrinsic pontine glioma.” She was subsequently treated with radiation and concurrent adjuvant temozolomide, but unfortunately there was minimal response and the patient died 6 months after diagnosis. Autopsy revealed an ETMR that was confirmed via C19MC fluorescence in situ hybridization and LIN28 immunohistochemistry. Although widespread central nervous system dissemination was observed, large portions of the main pontine mass exhibited evidence of extensive glial and neuronal maturation (ie, differentiation). We consider this tissue “maturation” to have been induced by chemotherapy and radiation. Herein, we discuss the importance of antemortem biopsy of intrinsic pontine tumors and the clinical significance of glial and neuronal maturation post therapy in the context of ETMR.

Malignant rhabdoid tumors and atypical teratoid/rhabdoid tumors of the central nervous system are primitive malignancies associated with a poor prognosis. These tumors have previously been characterized by inactivation of the switch/sucrose nonfermenting (SWI/SNF) chromatin remodeling complex protein integrase interactor 1 (INI1), encoded by the SMARCB1 gene. In the last decade, sporadic publications have shown that a different SWI/SNF protein, brahma-related gene 1 (BRG1), encoded by the SMARCA4 gene, is associated with a similar rhabdoid phenotype and possible germline mutation termed rhabdoid tumor predisposition syndrome type 2. We sought to determine the presence of BRG1 expression in pediatric embryonal tumors. Using a local tissue microarray consisting of 28 tumors diagnosed as having an undifferentiated, polyphenotypic, or rhabdoid morphology, expression of BRG1 by immunohistochemistry was performed. Four cases showed loss of INI1, while 3 of the remaining 24 cases demonstrated loss of BRG1. Two cases were diagnosed as soft tissue sarcomas, and 1 case was diagnosed as a small cell carcinoma of the ovary, hypercalcemic type. Survival ranged from less than 6 months after diagnosis to more than 5 years at the time of last follow-up. In conclusion, we demonstrate that BRG1 immunohistochemistry is a useful second-line immunostain for the workup of undifferentiated, polyphenotypic or rhabdoid pediatric tumors that demonstrate retained expression of INI1.

Pallister-Hall syndrome (PHS) is a rare malformative disorder that is due to truncating functional repressor mutations in GLI3. Since the seminal publication in 1980, hypothalamic tumors have been recognized to be a cardinal feature of PHS. In their original description of the neuropathologic features of PHS, Clarren et al. coined the term “hamartoblastoma” to characterize what they deemed to be a dual malformative and neoplastic mass of the hypothalamus. In subsequent published cases/series of PHS, the term “hamartoma” was often substituted for hamartoblastoma given what appeared to be a benign natural history of this lesion. Additional confusion in the literature has ensued since most hypothalamic hamartomas (HH) encountered on the clinical neuropathology service are “isolated” in nature (ie, no other congenital malformations) and present in a very different and stereotypical fashion with gelastic seizures and/or precocious puberty. While genomic investigations of isolated HH have begun to uncover a mutational profile of these cases, GLI3 mutations have only been recognized in a small subset of isolated HH. Herein, we describe the autopsy findings from a 21-week gestational age fetus with features of PHS. Moreover, we provide a detailed description of the hypothalamic tumor affecting this fetus and propose a novel subclassification of HH, distinguishing syndromic from isolated forms based upon the presence or absence of neocortical-like areas.

Congenital brain tumors are rare. Clinically, they often result in macrocrania, hydrocephalus, and focal neurologic deficits. Fetal onset may result in dystocia and stillbirth. Antenatal detection is becoming more common as the result of neuroimaging, and modalities such as magnetic resonance imaging can assist in narrowing the pathologic differential diagnoses. Teratomas and astrocytomas appear to be the most common congenital neoplasms. Amongst the latter, all grades and many subtypes are represented in the congenital time period, including the diffusely infiltrative forms of astrocytoma. Gliosarcoma is currently considered a variant of glioblastoma (i.e., astrocytoma, World Health Organization grade IV) that exhibits genetically similar yet phenotypically separate histologic regions of high-grade astrocytoma and sarcoma. Only rare instances of congenital gliosarcoma have been reported. We detail the case of a 1-day-old term male who presented with macrocrania, hydrocephalus, and signs of increased intracranial pressure. Pathology revealed evidence of a classic gliosarcoma.