To establish the frequency of IDH1 mutations in glioblastomas at a population level, and to assess whether they allow reliable discrimination between primary (de novo) glioblastomas and secondary ...glioblastomas that progressed from low-grade or anaplastic astrocytoma.
We screened glioblastomas from a population-based study for IDH1 mutations and correlated them with clinical data and other genetic alterations.
IDH1 mutations were detected in 36 of 407 glioblastomas (8.8%). Glioblastoma patients with IDH1 mutations were younger (mean, 47.9 years) than those with EGFR amplification (60.9 years) and were associated with significantly longer survival (mean, 27.1 versus 11.3 months; P < 0.0001). IDH1 mutations were frequent in glioblastomas diagnosed as secondary (22 of 30; 73%), but rare in primary glioblastomas (14 of 377; 3.7%: P < 0.0001). IDH1 mutations as genetic marker of secondary glioblastoma corresponded to the respective clinical diagnosis in 95% of cases. Glioblastomas with IDH1 mutation diagnosed as primary had clinical and genetic profiles similar to those of secondary glioblastomas, suggesting that they may have rapidly progressed from a less malignant precursor lesion that escaped clinical diagnosis and were thus misclassified as primary. Conversely, glioblastomas without IDH1 mutations clinically diagnosed as secondary typically developed from anaplastic rather than low-grade gliomas, suggesting that at least some were actually primary glioblastomas, that may have been misclassified, possibly due to histologic sampling error.
IDH1 mutations are a strong predictor of a more favorable prognosis and a highly selective molecular marker of secondary glioblastomas that complements clinical criteria for distinguishing them from primary glioblastomas.
IDH1 encodes isocitrate dehydrogenase 1, which participates in the citric acid cycle and was recently reported to be mutated in 12% of glioblastomas. We assessed IDH1 mutations in 321 gliomas of ...various histological types and biological behaviors. A total of 130 IDH1 mutations was detected, and all were located at amino acid residue 132. Of these, 91% were G→A mutations (Arg→His). IDH1 mutations were frequent in low-grade diffuse astrocytomas (88%) and in secondary glioblastomas that developed through progression from low-grade diffuse or anaplastic astrocytoma (82%). Similarly, high frequencies of IDH1 mutations were found in oligodendrogliomas (79%) and oligoastrocytomas (94%). Analyses of multiple biopsies from the same patient (51 cases) showed that there were no cases in which an IDH1 mutation occurred after the acquisition of either a TP53 mutation or loss of 1p/19q, suggesting that IDH1 mutations are very early events in gliomagenesis and may affect a common glial precursor cell population. IDH1 mutations were co-present with TP53 mutations in 63% of low-grade diffuse astrocytomas and with loss of heterozygosity 1p/19q in 64% of oligodendrogliomas; they were rare in pilocytic astrocytomas (10%) and primary glioblastomas (5%) and absent in ependymomas. The frequent presence of IDH1 mutations in secondary glioblastomas and their near-complete absence in primary glioblastomas reinforce the concept that despite their histological similarities, these subtypes are genetically and clinically distinct entities.
Desmoplastic myxoid tumor (DMT), SMARCB1-mutant is a recently proposed brain tumor that occurs in the pineal region of adults. This tumor is characterized by desmoplastic stroma and various degrees ...of myxoid matrix. Tumor cells with low-grade morphology show polyphenotypic immunoreactivity, and rhabdoid cells are rare. We herein present a case with some uncommon features such as no myxoid stroma and slightly elevated proliferating activity. To date, knowledge on the variety of SMARCB1/INI1-deficient tumors of the central nervous system is gradually increasing, encompassing highly aggressive to slow-growing varieties. DMT, SMARCB1-mutant seems to be relatively benign, but careful attention is necessary because SMARCB1/INI1 deficiency is generally a genetic signature of concern.
Pregnane X receptor (PXR) and constitutive androstane receptor (CAR) are nuclear receptors that are highly expressed in the liver and activated by numerous chemicals. While CAR activation by its ...activators, such as phenobarbital (PB), induces hepatocyte proliferation and liver carcinogenesis in rodents, it remains unclear whether PXR activation drives liver cancer. To investigate the influence of PXR activation on liver carcinogenesis, we treated mice with the PXR activator pregnenolone 16α-carbonitrile (PCN) with or without PB following tumor initiation with diethylnitrosamine (DEN). After 20 weeks of treatment, preneoplastic lesions detected by immunostaining with an anti-KRT8/18 antibody were observed in PB-treated but not PCN-treated mice, and PCN cotreatment augmented the formation of preneoplastic lesions by PB. After 35 weeks of treatment, macroscopic observations indicated that PB-treated and PB/PCN-cotreated mice had increased numbers of liver tumors compared to control and PCN-treated mice. In the pathological analyses of liver sections, all the mice in the PB and PB/PCN groups developed carcinoma and/or eosinophilic adenoma, but in the PB/PCN group, the multiplicity of carcinoma and eosinophilic adenoma was significantly reduced and the size of carcinoma showed a tendency to decrease. No mouse in the control or PCN-treated group developed such tumors. Differentially expressed gene (DEG) and gene set enrichment analyses in combination with RNA sequencing suggested the increased expression of genes related to epithelial–mesenchymal transition (EMT) in mice cotreated with PCN and PB compared to those treated with PB alone. Changes in the hepatic mRNA levels of epithelial marker genes supported the results of the transcriptome analyses. In conclusion, the present results suggest that PXR activation does not promote hepatocarcinogenesis in contrast to CAR and rather attenuates CAR-mediated liver cancer development by suppressing the EMT of liver cancer cells in rodents.
Epithelioid glioblastoma (E‐GBM) is a rare aggressive variant of IDH‐wildtype glioblastoma newly recognized in the 2016 World Health Organization classification, composed predominantly of monotonous, ...patternless sheets of round cells with laterally positioned nuclei and plump eosinophilic cytoplasm. Approximately 50% of E‐GBM harbor BRAF V600E, which is much less frequently found in other types of glioblastomas. Most E‐GBM are recognized as primary/de novo lesions; however, several E‐GBM with co‐ or pre‐existing lower‐grade lesions have been reported. To better understand associations between E‐GBM and the lower‐grade lesions, we undertook a histological and molecular analysis of 14 E‐GBM, 10 of which exhibited lower‐grade glioma‐like components (8 E‐GBM with co‐existing diffuse glioma‐like components, 1 E‐GBM with a co‐existing PXA‐like component and 1 E‐GBM with a pre‐existing PXA). Molecular results demonstrated that the prevalence of BRAF V600E, TERT promoter mutations and CDKN2A/B homozygous deletions in E‐GBM were 13/14 (93%), 10/14 (71%) and 11/14 (79%), respectively, and concurrent BRAF V600E, TERT promoter mutations and CDKN2A/B homozygous deletions were observed in 7/14 (50%) of E‐GBM. These alterations were also frequently seen in the lower‐grade lesions irrespective of the histology. Genetic analysis including array comparative genomic hybridization performed for 5 E‐GBM with co‐ and pre‐existing lower‐grade components revealed that all molecular changes found in the lower‐grade components were also observed in the E‐GBM components, and additional changes were detected in the E‐GBM components. In conclusion, E‐GBM frequently exhibit BRAF V600E, TERT promoter mutations and CDKN2A/B homozygous deletions and these alterations tend to coexist in E‐GBM. Taken together with the facts that only one PXA preceded E‐GBM among these lower‐grade lesions, and that co‐occurrence of BRAF V600E, TERT promoter mutations and CDKN2A/B homozygous deletions have been reported to be rare in conventional lower‐grade diffuse gliomas, the diffuse glioma‐like components may be distinct infiltrative components of E‐GBM, reflecting intratumoral heterogeneity.
Astroblastoma is a rare, enigmatic tumor of the central nervous system (CNS) which shares some clinicopathologic aspects with other CNS tumors, especially ependymoma. To further clarify the nature of ...astroblastoma, we performed clinicopathologic and molecular genetic studies on eight cases of astroblastoma. The median age of the patients was 14.5 years, ranging from 5 to 60 years, and seven of the patients were female. All tumors arose in the cerebral hemisphere and radiologically appeared to be well‐bordered, nodular tumors often associated with cystic areas and contrast‐enhancement. Six of the seven patients with prognosis data survived without recurrences during the follow‐up periods ranging from six to 76 months. One patient had multiple recurrences and died six years later. All tumors exhibited salient microscopic features, such as being well demarcated from the surrounding brain tissue, perivascular arrangement of epithelioid tumor cells (represented by “astroblastic” pseudorosettes, trabecular alignment, and pseudopapillary patterns), and hyalinized blood vessels. Immunoreactivity for GFAP, S‐100 protein, Olig2, and EMA was variably demonstrated in all tumors, and IDH1 R132H and L1CAM were negative. Array comparative genomic hybridization revealed numerous heterozygous deletions on chromosome X in the four tumors studied, and break‐apart fluorescence in situ hybridization demonstrated rearrangement of MN1 in five tumors with successful testing. The characteristic clinicopathologic and genetic findings support the idea that astroblastoma is distinct from other CNS tumors, in particular, ependymoma. In addition, MN1 rearrangement and aberrations of chromosome X may partly be involved in the pathogenesis of astroblastoma.
Epithelioid glioblastoma (E‐GBM) is a rare variant of glioblastoma (GBM), characterized by epithelioid cells with eosinophilic round cytoplasm devoid of stellate cytoplasmic processes. A number of ...studies have demonstrated that more than half of E‐GBMs harbor a valine to glutamic acid substitution at position 600 of the serine/threonine‐protein kinase BRAF (BRAF V600E). However, there are no previous reports on E‐GBM with telomerase reverse transcriptase (TERT) promoter mutation in addition to BRAF V600E mutation. Here, we report an E‐GBM case in an 18‐year‐old man with BRAF V600E and TERT promoter mutations. The tumor composed of 80% E‐GBM and 20% diffuse astrocytoma‐like components, and BRAF V600E and TERT promoter mutations were detected in both. E‐GBM generally arises as a primary lesion; however, a few previous cases have been demonstrated to accompany low‐grade areas. Demonstration of concurrent BRAF V600E and TERT promoter mutations in low‐ and high‐grade lesions strongly suggested their identical origin, and acquisition of each mutation may be an early event, possibly playing a pivotal role in the genesis and subsequent progression to E‐GBM.
Atypical teratoid/rhabdoid tumors (AT/RT) are rare, highly malignant neoplasms of the central nervous system that predominantly occur in infants, and are characterized by the presence of rhabdoid ...cells and inactivation of
INI1
or (extremely rarely)
BRG1
. The vast majority of AT/RT are recognized as primary tumors; however, rare AT/RT or INI1-deficient RT arising from other primary tumors have been reported. To better characterize secondary RT, we performed a histological and molecular analysis of four RT arising from pleomorphic xanthoastrocytoma (PXA), anaplastic PXA, low-grade astrocytoma, or ependymoma. Histologically, although conventional AT/RT are usually not largely composed of rhabdoid cells, three secondary RT were composed mainly of rhabdoid cells, two of which arising from (anaplastic) PXA exhibited marked nuclear pleomorphism reminiscent of that in the precursor lesions. Regarding
INI1
alterations, although mutations including small indels are frequent in conventional AT/RT, only in one secondary RT had a mutation. Moreover, together with previously reported cases, biallelic
INI1
inactivation in secondary RT was mostly due to biallelic focal and/or broad deletions. Although conventional AT/RT have stable chromosomal profiles, i.e., the frequency of copy number changes involving chromosomes other than chromosome 22 is remarkably low, our array comparative genomic hybridization analysis revealed numerous copy number changes in the secondary RT. In conclusion, secondary RT of the central nervous system are clinicopathologically and molecularly different from conventional pediatric AT/RT, and a nosological issue is whether these secondary RT should be called secondary “AT/RT” as most of the reported cases were.
An 82‐year‐old man, who was healthy and had worked as a farmer, experienced worsening neurological symptoms over a seven‐month period, which eventually caused his death. Multiple fluctuating brain ...lesions were detected radiographically. Clinically, sarcoidosis was ranked high among the differential diagnoses because of the presence of skin lesions showing granulomatous inflammation, confirmed by biopsy. The patient's cerebrospinal fluid was also examined, but no definitive diagnosis was made while he was alive. An autopsy revealed multiple granulomatous amebic encephalitis lesions in the brain. Genetic and immunohistochemical analyses identified Balamuthia (B.) mandrillaris, a free‐living ameba, which resides in soil and fresh water, as the causative organism. A retrospective examination revealed B. mandrillaris in the biopsied skin as well as cerebrospinal fluid, strongly suggesting that the ameba had spread into the brain percutaneously. Few studies have detailed the cutaneous pathology of B. mandrillaris infections. In general, granulomatous amebic encephalitis is extremely difficult to diagnose without autopsy, but the present case provides a clue that could allow similar cases to be diagnosed earlier; that is, the presence of skin lesions.
Atypical teratoid/rhabdoid tumors (AT/RT) are rare, aggressive, embryonal brain tumors that occur most frequently in very young children; they are characterized by rhabdoid cells and loss of INI1 ...protein nuclear expression. Here, we report the case of a 24-year-old man with a left frontal lobe tumor that was composed mainly of rhabdoid cells showing loss of INI1 nuclear reactivity and polyphenotypic immunohistochemical expression, with a small INI1-positive component of ependymoma. Array comparative genomic hybridization separately conducted for each histologically distinct component revealed 22 shared identical copy number alterations, including loss of heterozygosity of chromosome 22q containing the INI1 locus. Furthermore, we found the C11orf95-RELA fusion gene, the genetic hallmark of supratentorial ependymomas, not only in the ependymoma component but also in the AT/RT component by fluorescence in situ hybridization analysis, suggesting that the AT/RT cells secondarily progressed from the preexisting ependymoma cells. A second genetic inactivating event in the INI1 gene was not detected in the AT/RT component. There are several reported cases of AT/RT (or INI1-negative rhabdoid tumors) arising in the setting of other primary brain tumors (gangliogliomas, pleomorphic xanthoastrocytomas, and high-grade gliomas), but the present case is the first reported AT/RT apparently evolving from an ependymoma.
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