PRC2 disruption in cerebellar progenitors produces cerebellar hypoplasia and aberrant myoid differentiation without blocking medulloblastoma growth.

We show that Polycomb Repressive Complex-2 (PRC2) components EED and EZH2 maintain neural identity in cerebellar granule neuron progenitors (CGNPs) and SHH-driven medulloblastoma, a cancer of CGNPs. Proliferating CGNPs and medulloblastoma cells inherit neural fate commitment through epigenetic mechanisms. The PRC2 is an epigenetic regulator that has been proposed as a therapeutic target in medulloblastoma. To define PRC2 function in cerebellar development and medulloblastoma, we conditionally deleted PRC2 components Eed or Ezh2 in CGNPs and analyzed medulloblastomas induced in Eed-deleted and Ezh2-deleted CGNPs by expressing SmoM2, an oncogenic allele of Smo. Eed deletion destabilized the PRC2, depleting EED and EZH2 proteins, while Ezh2 deletion did not deplete EED. Eed-deleted cerebella were hypoplastic, with reduced proliferation, increased apoptosis, and inappropriate muscle-like differentiation. Ezh2-deleted cerebella showed similar, milder phenotypes, with fewer muscle-like cells and without reduced growth. Eed-deleted and Ezh2-deleted medulloblastomas both demonstrated myoid differentiation and progressed more rapidly than PRC2-intact controls. The PRC2 thus maintains neural commitment in CGNPs and medulloblastoma, but is not required for SHH medulloblastoma progression. Our data define a role for the PRC2 in preventing inappropriate, non-neural fates during postnatal neurogenesis, and caution that targeting the PRC2 in SHH medulloblastoma may not produce durable therapeutic effects.

Congress of neurological surgeons systematic review and evidence-based guidelines update on the role of neuropathology in the management of progressive glioblastoma in adults.

TARGET POPULATION: These recommendations apply to adult patients with progressive or recurrent glioblastoma (GBM). QUESTION: For adult patients with progressive glioblastoma does testing for Isocitrate Dehydrogenase (IDH) 1 or 2 mutations provide new additional management or prognostic information beyond that derived from the tumor at initial presentation? RECOMMENDATION: Level III: Repeat IDH mutation testing is not necessary if the tumor is histologically similar to the primary tumor and the patient's clinical course is as expected. QUESTION: For adult patients with progressive glioblastoma does repeat testing for MGMT promoter methylation provide new or additional management or prognostic information beyond that derived from the tumor at initial presentation and what methods of detection are optimal? RECOMMENDATION: Level III: Repeat MGMT promoter methylation is not recommended. QUESTION: For adult patients with progressive glioblastoma does EGFR amplification or mutation testing provide management or prognostic information beyond that provided by histologic analysis and if performed on previous tissue samples, does it need to be repeated? RECOMMENDATION: Level III: In cases that are difficult to classify as glioblastoma on histologic features EGFR amplification testing may help in classification. If a previous EGFR amplification was detected, repeat testing is not necessary. Repeat EGFR amplification or mutational testing may be recommended in patients in which target therapy is being considered. QUESTION: For adult patients with progressive glioblastoma does large panel or whole genome sequencing provide management or prognostic information beyond that derived from histologic analysis? RECOMMENDATION: Level III: Primary or repeat large panel or whole genome sequencing may be considered in patients who are eligible or interested in molecularly guided therapy or clinical trials. QUESTION: For adult patients with progressive glioblastoma should immune checkpoint biomarker testing be performed to provide management and prognostic information beyond that obtained from histologic analysis? RECOMMENDATION: Level III: The current evidence does not support making PD-L1 or mismatch repair (MMR) enzyme activity a component of standard testing. QUESTION: For adult patients with progressive glioblastoma are there meaningful biomarkers for bevacizumab responsiveness and does their assessment provide additional information for tumor management and prognosis beyond that learned by standard histologic analysis? RECOMMENDATION: Level III: No established Bevacizumab biomarkers are currently available based upon the inclusion criteria of this guideline.

Ingested Foreign Bodies Can Cause Appendicitis and Perforation: A Multi-Institutional Case Series.

INTRODUCTION: Appendicular foreign bodies are a rare, under-described cause of appendicitis. We performed this study to determine the varied causes and consequences of foreign-body appendicitis. METHODS: On retrospective review of the pathology archives of seven institutions, we identified 56 appendix specimens containing a foreign body (defined as ingested, non-digestible material). We recorded the type of foreign body, patient age and sex, and other findings, as available. RESULTS: Mean patient age was 7.7 years (range: 1 day-18 years). The foreign bodies included hair, plant material, magnets, other metallic material, BB pellets, foreign material not otherwise specified, and other miscellaneous objects. Of 48 cases with available clinical information, 31 patients presented with abdominal pain, and 22 were preoperatively diagnosed as having appendicitis/appendicular inflammation. Seven patients had appendiceal perforation (13%). The foreign body was grossly identified in 34/47 cases with available gross descriptions. Twenty-seven cases had an identifiable foreign body microscopically; 10 were associated with giant cell reaction. DISCUSSION: Hair and plant materials were the most common foreign objects found in the appendix; they often cause mucosal damage and giant cell reaction. Metallic objects were less common. Although appendicular foreign bodies in children are rare and sometimes asymptomatic, they may lead to perforation.

MRI Imaging Characteristics of Glioblastoma with Concurrent Gain of Chromosomes 19 and 20.

Glioblastoma (GBM) is the most common and deadly primary brain tumor in adults. Some of the genetic variations identified thus far, such as IDH mutation and MGMT promotor methylation, have implications for survival and response to therapy. A recent analysis of long-term GBM survivors showed that concurrent gain of chromosomes 19 and 20 (19/20 co-gain) is a positive prognostic factor that is independent of IDH mutation status. In this study, we retrospectively identified 18 patients with 19/20 co-gain and compared their imaging features to a control cohort without 19/20 co-gain. Imaging features such as tumor location, size, pial invasion, and ependymal extension were examined manually. When compared without further genetic subclassification, both groups showed similar imaging features except for rates of pial invasion. When each group was subclassified by MGMT promotor methylation status however, the two groups showed different imaging features in a number of additional ways including tumor location, size, and ependymal extension. Our results indicate that different permutations of various genetic mutations that coexist in GBM may interact in unpredictable ways to affect imaging appearance, and that imaging prognostication may be better approached in the context of the global genomic profile rather than individual genetic alterations.

Congenital Myenteric Hypoganglionosis.

Congenital myenteric hypoganglionosis is a rare developmental disorder characterized clinically by severe and persistent neonatal intestinal pseudoobstruction. The diagnosis is established by the prevalence of small myenteric ganglia composed of closely spaced ganglion cells with sparse surrounding neuropil. In practice, the diagnosis entails familiarity with the normal appearance of myenteric ganglia in young infants and the ability to confidently recognize significant deviations in ganglion size and morphology. We review clinical, histologic, and immunohistochemical findings from 12 patients with congenital myenteric hypoganglionosis in comparison with similar data from age-matched controls and clearly delineate the diagnostic features of the condition. Practical guidelines are provided to assist surgical pathologists, who are likely to encounter this condition only infrequently. The diagnosis typically requires full-thickness intestinal biopsy as the abnormality is confined to the myenteric plexus in many patients. Immunohistochemistry for Hu C/D may be used to confirm hypoganglionosis. Reduced staining for calretinin and NeuN implicates a selective deficiency of intrinsic primary afferent neurons in this disease.

The role of neuropathology in the management of newly diagnosed glioblastoma: a systematic review and evidence-based clinical practice guideline.

TARGET POPULATION: These recommendations apply to adult patients with newly diagnosed or suspected glioblastoma (GBM) QUESTION : For adult patients with newly diagnosed GBM does testing for Isocitrate Dehydrogenase 1 or 2 (IDH 1/2) mutations afford benefit beyond standard histopathology in providing accurate classification and outcome prognostication? Level III IDH 1/2 mutational status by immunohistochemistry (IHC) and/or sequencing is suggested for classification and prognostic information. Level III Non-canonical IDH 1/2 mutations are very rare in patients aged 55 or older and universal testing of variant mutations by sequence analysis is not suggested for this age range. QUESTION: For adult patients with lower grade infiltrating astrocytomas (WHO grades II and III) can the IDH-wildtype status designation supersede histopathology to predict prognosis and biologic relevance to eventual behavior as a GBM? Level III The designation of infiltrating astrocytomas (WHO grades II and III) as IDH-wildtype is not suggested as sufficient for a higher grade designation alone. Level III It is suggested that IDH-wildtype WHO grades II and III astrocytomas be tested for molecular-genetic alterations typical of IDH-wildtype GBM such as EGFR amplification, gain of chromosome 7/loss of chromosome 10 and TERT-p mutation to substantiate prediction of behavior similar to IDH-wildtype glioblastoma. Level III It is suggested that a diagnosis of diffuse astrocytic glioma, IDH-wildtype, with molecular features of GBM, WHO grade IV be rendered for infiltrating astrocytomas that lack histologic criteria of GBM but harbors molecular-genetic alterations of IDH-wildtype glioblastoma. QUESTION: For adult patients with newly diagnosed infiltrating glioma arising in the midline does testing for H3-K27M mutations provide information beyond that gained by histopathology for accurate classification and outcome prognostication? Level III It is suggested that infiltrating gliomas arising in midline anatomic locations be tested for the H3-K27M mutation as they tend to exhibit WHO grade IV behavior even if they lack histologic criteria for glioblastoma.

Subtype and grade-dependent spatial heterogeneity of T-cell infiltration in pediatric glioma.

Brain tumors are the leading cause of cancer-related mortality in children and have distinct genomic and molecular features compared with adult glioma. However, the properties of immune cells in these tumors has been vastly understudied compared with their adult counterparts. We combined multiplex immunofluorescence immunohistochemistry coupled with machine learning and single-cell mass cytometry to evaluate T-cells infiltrating pediatric glial tumors. We show that low-grade tumors are characterized by greater T-cell density compared with high-grade glioma (HGG). However, even among low-grade tumors, T-cell infiltration can be highly variable and subtype-dependent, with greater T-cell density in pleomorphic xanthoastrocytoma and ganglioglioma. CD3+ T-cell infiltration correlates inversely with the expression of SOX2, an embryonal stem cell marker commonly expressed by glial tumors. T-cells within both HGG and low-grade glioma (LGG) exhibit phenotypic heterogeneity and tissue-resident memory T-cells consist of distinct subsets of CD103+ and TCF1+ cells that exhibit distinct spatial localization patterns. TCF1+ T-cells are located closer to the vessels while CD103+ resident T-cells reside within the tumor further away from the vasculature. Recurrent tumors are characterized by a decline in CD103+ tumor-infiltrating T-cells. BRAFV600E mutation is immunogenic in children with LGG and may serve as a target for immune therapy. These data provide several novel insights into the subtype-dependent and grade-dependent changes in immune architecture in pediatric gliomas and suggest that harnessing tumor-resident T-cells may be essential to improve immune control in glioma.

Embryonal Rhabdomyosarcoma of the Ovary and Fallopian Tube: Rare Neoplasms Associated With Germline and Somatic DICER1 Mutations.

DICER1 mutations (somatic or germline) are associated with a variety of uncommon neoplasms including cervical and genitourinary embryonal rhabdomyosarcoma (ERMS). We report a primary ovarian and 2 primary fallopian tube ERMS occurring in 60-, 13-, and 14-year-olds, respectively. The 3 neoplasms exhibited a similar morphologic appearance being polypoid and containing edematous hypocellular areas and hypercellular foci composed of small cells with scant cytoplasm exhibiting rhabdomyoblastic differentiation (desmin, myogenin, myoD1 positive). There was cellular cartilage in all cases and extensive foci of anaplasia, eosinophilic globules, and bone/osteoid in 1 case each. All 3 neoplasms exhibited DICER1 mutations; in 1 of the tubal cases, the patient had a germline mutation and in the other 2 cases, the DICER1 mutations were somatic. Accompanying DICER1 "second hits" were identified in all cases. In 2 of the neoplasms, SALL4-positive glandular structures were present which we speculate may represent an unusual primitive "metaplastic" phenomenon. Our study adds to the literature on ERMS at unusual sites associated with DICER1 mutations. ERMS arising at such sites, especially when they contain cartilage or bone/osteoid, are especially likely to be associated with DICER1 mutations. Pathologists should be aware of this as these may be the sentinel neoplasms in patients with DICER1 syndrome and confirming a germline mutation can facilitate the screening of the individual and affected family members for other neoplasms which occur in this syndrome.

Metastatic Renal Cell Carcinoma to the Brain: A Contemporary Clinicopathologic Analysis With Comparison of Immunohistochemical Profiles to Selected Primary Brain Tumors With Clear Cell Features.

Brain metastases from renal cell carcinoma (RCC) are associated with significant morbidity and mortality. However, there are only few large series in the pathology literature specifically analyzing the clinicopathologic and immunohistochemical features in comparison with primary brain tumors with clear cell features. We identified 34 cases of metastatic RCC to the brain from the Urologic Pathology and Neuropathology files of 2 institutions between 2000 and 2018. Mean patient age at diagnosis of primary RCC was 59 years (range: 37 to 82 y). The mean size of 34 primary RCC was 7.9 cm (range: 2.5 to 19.5 cm). Twenty of 34 (59%) cases of brain metastases had primary RCC categorized as pT3. Brain imaging showed a solitary, well circumscribed, enhancing lesion in 18 of 34 (53%) patients and multifocal lesions in 16 of 34 (47%) patients. The mean size of metastatic RCC to the brain was 2.3 cm (range: 0.3 to 5.5 cm). Fifteen of 34 (44%) cases had isolated brain metastases and 19 of 34 (56%) cases had concomitant extracerebral metastases. The histologic subtypes were clear cell RCC 29 of 34 (85%) cases, RCC unclassified 4 of 34 (12%) cases, and papillary RCC 1 of 34 (3%) cases. We also included primary brain tumors with clear cell features including hemangioblastoma (30 cases), microcystic meningioma (11 cases), and clear cell meningioma (3 cases). The utility of an immunohistochemical panel that includes PAX8, carbonic anhydrase IX, SST2Ra, and inhibin is very useful in the distinction of these entities in a subset of patients.

Human Mesenchymal glioblastomas are characterized by an increased immune cell presence compared to Proneural and Classical tumors.

Glioblastoma (GBM) is the most aggressive malignant primary brain tumor in adults, with a median survival of 14.6 months. Recent efforts have focused on identifying clinically relevant subgroups to improve our understanding of pathogenetic mechanisms and patient stratification. Concurrently, the role of immune cells in the tumor microenvironment has received increasing attention, especially T cells and tumor-associated macrophages (TAM). The latter are a mixed population of activated brain-resident microglia and infiltrating monocytes/monocyte-derived macrophages, both of which express ionized calcium-binding adapter molecule 1 (IBA1). This study investigated differences in immune cell subpopulations among distinct transcriptional subtypes of GBM. Human GBM samples were molecularly characterized and assigned to Proneural, Mesenchymal or Classical subtypes as defined by NanoString nCounter Technology. Subsequently, we performed and analyzed automated immunohistochemical stainings for TAM as well as specific T cell populations. The Mesenchymal subtype of GBM showed the highest presence of TAM, CD8+, CD3+ and FOXP3+ T cells, as compared to Proneural and Classical subtypes. High expression levels of the TAM-related gene AIF1, which encodes the TAM-specific protein IBA1, correlated with a worse prognosis in Proneural GBM, but conferred a survival benefit in Mesenchymal tumors. We used our data to construct a mathematical model that could reliably identify Mesenchymal GBM with high sensitivity using a combination of the aforementioned cell-specific IHC markers. In conclusion, we demonstrated that molecularly distinct GBM subtypes are characterized by profound differences in the composition of their immune microenvironment, which could potentially help to identify tumors amenable to immunotherapy.

The impact of histopathology and NAB2-STAT6 fusion subtype in classification and grading of meningeal solitary fibrous tumor/hemangiopericytoma.

Meningeal solitary fibrous tumor (SFT)/hemangiopericytoma (HPC) is a rare tumor with propensity for recurrence and metastasis. Although multiple classification schemes have been proposed, optimal risk stratification remains unclear, and the prognostic impact of fusion status is uncertain. We compared the 2016 WHO CNS tumor grading scheme (CNS-G), a three-tier system based on histopathologic phenotype and mitotic count, to the 2013 WHO soft-tissue counterpart (ST-G), a two-tier system based on mitotic count alone, in a cohort of 133 patients [59 female, 74 male; mean age 54 years (range 20-87)] with meningeal SFT/HPC. Tumors were pathologically confirmed through review of the first tumor resection (n = 97), local recurrence (n = 35), or distant metastasis (n = 1). A STAT6 immunostain showed nuclear expression in 132 cases. NAB2-STAT6 fusion was detected in 99 of 111 successfully tested tumors (89%) including the single STAT6 immunonegative tumor. Tumors were classified by CNS-G as grade 1 (n = 43), 2 (n = 41), or 3 (n = 49), and by ST-G as SFT (n = 84) or malignant SFT (n = 49). Necrosis was present in 16 cases (12%). On follow-up, 42 patients had at least one subsequent recurrence or metastasis (7 metastasis only, 33 recurrence only, 2 patients had both). Twenty-nine patients died. On univariate analysis, necrosis (p = 0.002), CNS-G (p = 0.01), and ST-G (p = 0.004) were associated with recurrence-free (RFS) but not overall survival (OS). NAB2-STAT6 fusion type was not significantly associated with RFS or OS, but was associated with phenotype. A modified ST-G incorporating necrosis showed higher correlation with RFS (p = 0.0006) and remained significant (p = 0.02) when considering only the primary tumors. From our data, mitotic rate and necrosis appear to stratify this family of tumors most accurately and could be incorporated in a future grading scheme.

Predicting cancer outcomes from histology and genomics using convolutional networks.

Cancer histology reflects underlying molecular processes and disease progression and contains rich phenotypic information that is predictive of patient outcomes. In this study, we show a computational approach for learning patient outcomes from digital pathology images using deep learning to combine the power of adaptive machine learning algorithms with traditional survival models. We illustrate how these survival convolutional neural networks (SCNNs) can integrate information from both histology images and genomic biomarkers into a single unified framework to predict time-to-event outcomes and show prediction accuracy that surpasses the current clinical paradigm for predicting the overall survival of patients diagnosed with glioma. We use statistical sampling techniques to address challenges in learning survival from histology images, including tumor heterogeneity and the need for large training cohorts. We also provide insights into the prediction mechanisms of SCNNs, using heat map visualization to show that SCNNs recognize important structures, like microvascular proliferation, that are related to prognosis and that are used by pathologists in grading. These results highlight the emerging role of deep learning in precision medicine and suggest an expanding utility for computational analysis of histology in the future practice of pathology.

Incorporating Advances in Molecular Pathology Into Brain Tumor Diagnostics.

Recent advances in molecular pathology have reshaped the practice of brain tumor diagnostics. The classification of gliomas has been restructured with the discovery of isocitrate dehydrogenase (IDH) 1/2 mutations in the vast majority of lower grade infiltrating gliomas and secondary glioblastomas (GBM), with IDH-mutant astrocytomas further characterized by TP53 and ATRX mutations. Whole-arm 1p/19q codeletion in conjunction with IDH mutations now define oligodendrogliomas, which are also enriched for CIC, FUBP1, PI3K, NOTCH1, and TERT-p mutations. IDH-wild-type (wt) infiltrating astrocytomas are mostly primary GBMs and are characterized by EGFR, PTEN, TP53, NF1, RB1, PDGFRA, and CDKN2A/B alterations, TERT-p mutations, and characteristic copy number alterations including gains of chromosome 7 and losses of 10. Other clinically and genetically distinct infiltrating astrocytomas include the aggressive H3K27M-mutant midline gliomas, and smaller subsets that occur in the setting of NF1 or have BRAF V600E mutations. Low-grade pediatric gliomas are both genetically and biologically distinct from their adult counterparts and often harbor a single driver event often involving BRAF, FGFR1, or MYB/MYBL1 genes. Large scale genomic and epigenomic analyses have identified distinct subgroups of ependymomas tightly linked to tumor location and clinical behavior. The diagnosis of embryonal neoplasms also integrates molecular testing: (I) 4 molecularly defined, biologically distinct subtypes of medulloblastomas are now recognized; (II) 3 histologic entities have now been reclassified under a diagnosis of "embryonal tumor with multilayered rosettes (ETMR), C19MC-altered"; and (III) atypical teratoid/rhabdoid tumors (AT/RT) now require SMARCB1 (INI1) or SMARCA4 (BRG1) alterations for their diagnosis. We discuss the practical use of contemporary biomarkers for an integrative diagnosis of central nervous system neoplasia.

Chordoid glioma of the third ventricle: report of a rapidly progressive case.

Chordoid gliomas are slowly growing third ventricular tumors that can be challenging to manage clinically. Rapid progression causing death has not been previously reported for this tumor type. We present and discuss a case of chordoid glioma that arose in a 46-year-old female who presented with progressive fatigue, headache, and altered mental status, attributable to severe hydrocephalus caused by a third ventricular mass. She underwent urgent subtotal resection and ventriculo-peritoneal shunt placements. Post-operative MRI noted residual tumor in the anterior resection cavity. An MRI performed 9 weeks later showed substantial progression, with marked tumor enlargement and compression of adjacent hypothalamic structures and the optic chiasm. Despite a course of radiation therapy, the tumor continued to enlarge, and the patient died from tumor progression 7 months after initial presentation. Post-mortem exam demonstrated a mass that expanded the third ventricle and compressed adjacent hypothalamic, thalamic and suprasellar structures. Histologic and immunohistochemical studies confirmed a chordoid glioma and revealed multifocal coagulative necrosis and intravascular thrombosis, which are unusual in this tumor type. Cytogenomic microarray testing revealed numerous DNA copy number abnormalities, many of which had not previously been reported in this tumor. The pathologic and cytogenetic changes may correlate with the aggressive behavior of this chordoid glioma and can be pursued by future investigation of additional cases.

Microcystic meningioma of the calvarium: a series of 9 cases and review of the literature.

Meningiomas are one of the most common tumors that arise within the central nervous system; they represent up to 30% of all primary intracranial tumors. Extradural meningiomas are rare (<2% of all meningiomas), and most arise within the calvarium. Intraosseous calvarial meningiomas are usually easy to diagnose histologically if they are of the meningothelial type; however, they may cause diagnostic challenges when they manifest as unusual morphologic variants, such as the microcystic type. To address this issue we present a series of 9 cases of calvarial microcystic meningiomas arising in 7 female and 2 male patients; all patients were adults. The tumors had heterogenous findings on imaging studies and ranged in size from 1.1 to 4.3 cm in greatest dimension. The neoplasms were composed predominantly of stellate and spindle cells with long, thin interconnecting cytoplasmic processes arranged in a complex network. The resulting cellular architecture was "sieve-like" in appearance because of the formation of numerous small "cyst-like" spaces interposed between the cytoplasmic processes of the tumor cells. All of the neoplasms expressed the characteristic immunophenotype of meningiomas (EMA, PR positive). Most tumors were resected, and none of these have recurred during a follow-up period of 1 to 83 months (average 17 mo). The morphology of the tumors and their anatomic location generated problems in diagnosis, especially in 6 patients with a history of malignancy and for whom metastatic disease was suspected clinically. Intraosseous microcystic meningioma is uncommon, and this series, the largest reported to date, describes their clinicopathologic findings, biological behavior, and features that facilitate their accurate diagnosis.