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We previously reported that there was a subgroup of IDH-mutated astrocytomas harboring only 19q-loss showing oligodendroglioma-like morphology and significantly longer overall survival (OS) compared with 19q-intact astrocytomas. The aim of this study was to further explore the biological characteristics of this possible subgroup and obtain insight into the mechanism of their relatively benign clinical behavior. We compared gene expression pattern between five 19q-loss and five 19q-intact IDH-mutated astrocytomas by microarray analysis. By comparing expression levels of genes of 19q-loss astrocytomas to those of 19q-intact astrocytomas, 102 up-regulated genes and 162 down-regulated genes were extracted. The down-regulated genes clustered heavily to 19q and 4p while the up-regulated genes clustered to 4q. It was noteworthy that fibroblast growth factor 1 associated with stem cell maintenance and multiple genes associated with glioma progression were down-regulated in 19q-loss astrocytomas, and these results were validated with the independent TCGA data set. On t-SNE analysis of the 19q-loss astrocytomas with other IDH-mutant glioma subgroups from the TCGA datasets, the expression pattern of the 19q-loss astrocytomas showed no shift toward oligodendrogliomas with 1p/19q codeletion but rather constituted a subgroup of astrocytoma. These findings suggested that 19q-loss in astrocytomas is more likely acquired event rather than an early event in oncogenesis like the 1p/19q-codeletion in oligodendrogliomas, and that the biological features of 19q-loss astrocytomas are possibly related to differentially expressed genes associated with stem cell maintenance and glioma progression.

Immunohistochemical staining is important for histological diagnosis of brain tumors; however, its intraoperative application has rarely been reported. Herein, we describe our methods and four successfully diagnosed cases. Between January 2008 and April 2010, intraoperative immunohistochemical analysis was performed in 43 patients undergoing brain tumor surgery at our institute. The time for rapid histological diagnosis was 70 min. MIB-1 immunostaining was performed; staining index (SI) was 0.8-76.2% (median, 2.5%) in rapid diagnoses and 0.6-83.9% (median, 7.7%) in permanent diagnoses. There was no discrepancy in low- or high-grade tumors between intraoperative and final pathological diagnosis. The antibodies used for staining were MIB-1 in all cases, L26 in 8 cases, UCHL-1 in 6 cases, GFAP in 4 cases, AFP in 3 cases, and PLAP in 5 cases. The staining patterns were similar between rapid and permanent diagnoses. We think that immunohistochemical examination is indicated under the following conditions: (1) preoperative radiologic differential diagnosis includes both high- and low-grade tumors, (2) intraoperative assessment is necessary to determine the extent of excision, and (3) quick and accurate pathological diagnosis is necessary for early initiation of treatment after surgery.

We report a basal ganglion hamartoma in a 10-year-old boy in whom the major clinical feature was precocious puberty. Endocrinological evaluation showed a gonadotropin reaction to luteinizing hormone-releasing hormone with no elevation of the human chorionic gonadotropin beta-subunit level in the serum or cerebrospinal fluid. Neuroimaging studies showed a small, calcified, nonenhanced mass lesion with some cystic components in the right basal ganglion. Histopathological examination of specimens removed by stereotactic needle biopsy revealed disorganized neuronal and glial elements in the calcified gray matter-like lesion. In addition, although the presence of microcalcifications was not conspicuous, similar neuroglial lesions of various sizes were scattered in the surrounding white matter. Immunostaining for Ki-67 antigen (MIB-1) showed very low proliferative potential of the glial cells in all the lesions. To our knowledge, this is the first reported occurrence of an intracranial hamartoma located in a site other than the hypothalamus and causing precocious puberty. The possible mechanisms underlying the development of precocious puberty in this patient are discussed.