Neuropathology Practice Research Articles

Current situation of neuropathology in Central America.

The present situation of neuropathology practice in the Central American region has not been addressed in the past. These are low middle-income countries, and therefore, many do not have a basic immunohistochemistry panel. Cytogenetics and molecular studies are not available in most of Central America. Pediatric brain tumors are diagnosed either by anatomical pathologists or by pediatric pathologists. Access to a weakly Latin American Tumor Board is available to consult cases, but most countries do not participate in these expert meetings. The most recent World Health Organization brain tumor book has a very broad molecular classification of pediatric brain tumors. All these factors make it very difficult to properly diagnose pediatric brain tumors in the region, and this impacts the treatment and overall survival of children with brain tumors.

Alzheimer's Disease as a Membrane Dysfunction Tauopathy? New Insights into the Amyloid Cascade Hypothesis.

The amyloid cascade hypothesis postulates that extracellular deposits of amyloid β (Aβ) are the primary and initial cause leading to the full development of Alzheimer's disease (AD) with intracellular neurofibrillary tangles; however, the details of this mechanism have not been fully described until now. Our preliminary data, coming from our day-to-day neuropathology practice, show that the primary location of the hyperphosphorylated tau protein is in the vicinity of the cell membrane of dystrophic neurites. This observation inspired us to formulate a hypothesis that presumes an interaction between low-density lipoprotein receptor-related protein 1 (LRP1) and fibrillar aggregates of, particularly, Aβ42 anchored at the periphery of neuritic plaques, making internalization of the LRP1-Aβ42 complex infeasible and, thus, causing membrane dysfunction, leading to the tauopathy characterized by intracellular accumulation and hyperphosphorylation of the tau protein. Understanding AD as a membrane dysfunction tauopathy may draw attention to new treatment approaches not only targeting Aβ42 production but also, perhaps paradoxically, preventing the formation of LRP1-Aβ42.

CIMPACT-NOW Update 8: Clarifications on molecular risk parameters and recommendations for WHO grading of meningiomas.

Meningiomas are the most frequent primary intracranial tumors. Hence, they constitute a major share of diagnostic specimens in neuropathology practice. The 2021 WHO Classification of Central Nervous System Tumors ("CNS5") has introduced the first molecular grading parameters for meningioma with oncogenic variants in the TERT promoter and homozygous deletion of CDKN2A/B as markers for CNS WHO grade 3. However, after publication of the new classification volume, clarifications were requested, not only on novel but also on long-standing questions in meningioma grading that were beyond the scope of the WHO "blue book". In addition, more recent research into possible new molecular grading parameters could not yet be implemented in the 2021 classification but constitute a compelling body of literature. Hence, the cIMPACT-NOW Steering Committee convened a working group to provide such clarification and assess the evidence of possible novel molecular criteria. As a result, this cIMPACT-NOW update provides guidance for more standardized morphological evaluation and interpretation, most prominently pertaining to brain invasion, identifies scenarios in which advanced molecular testing is recommended, proposes to assign CNS WHO grade 2 for cases with CNS WHO grade 1 morphology but chromosomal arm 1p deletion in combination with 22q deletion and/or NF2 oncogenic variants, and discusses areas in which the current evidence is not yet sufficient to result in new recommendations.

Pediatric neuropathology practice in a low- and middle-income country: capacity building through institutional twinning.

Accurate and precise diagnosis is central to treating central nervous system (CNS) tumors, yet tissue diagnosis is often a neglected focus in low- and middle-income countries (LMICs). Since 2016, the WHO classification of CNS tumors has increasingly incorporated molecular biomarkers into the diagnosis of CNS tumors. While this shift to precision diagnostics promises a high degree of diagnostic accuracy and prognostic precision, it has also resulted in increasing divergence in diagnostic and management practices between LMICs and high-income countries (HICs). Pathologists and laboratory professionals in LMICs lack the proper training and tools to join the molecular diagnostic revolution. We describe the impact of a 7-year long twinning program between Canada and Pakistan on pathology services. During the study period, 141 challenging cases of pediatric CNS tumors initially diagnosed at Aga Khan University Hospital (AKUH), Karachi, were sent to the Hospital for Sick Children in Toronto, Canada (SickKids), for a second opinion. Each case received histologic review and often immunohistochemical staining and relevant molecular testing. A monthly multidisciplinary online tumor board (MDTB) was conducted to discuss the results with pathologists from both institutions in attendance. Diagnostic discordance was seen in 30 cases. Expert review provided subclassification for 53 cases most notably for diffuse gliomas and medulloblastoma. Poorly differentiated tumors benefited the most from second review, mainly because of the resolving power of specialized immunohistochemical stains, NanoString, and targeted gene panel next-generation sequencing. Collaboration with expert neuropathologists led to validation of over half a dozen immunostains at AKUH facilitating diagnosis of CNS tumors. LMIC-HIC Institutional twinning provides much-needed training and mentorship to pathologists and can help in infrastructure development by adopting and validating new immunohistochemical stains. Persistent unresolved cases indicate that molecular techniques are indispensable in for diagnosis in a minority of cases. The development of affordable alternative molecular techniques may help with these histologically unresolved cases.

In Situ Hybridization of Brain Slices.

In situ hybridization (ISH) is an important technique for identifying gene expression at the cellular level in various organs, including brain slices. This approach hybridizes nucleic acid probes to cellular mRNA, allowing the detection of transcriptional products. Recent advances have enabled RNA preservation in formalin-fixed paraffin-embedded (FFPE) samples, making ISH applicable to brain tumor diagnosis and research. Here, we provide a concise overview of the standard application of chromogenic ISH in neuroscience research and neuropathology practice using FFPE blocks of brain slice sections.

Diagnostic Value of Smears and Frozen Sections in Neuropathology Practice: Institutional Experience

Diagnostic Value of Smears and Frozen Sections in Neuropathology Practice: Institutional Experience

A Contemporary Approach to Intraoperative Evaluation in Neuropathology.

Although the basic principles of intraoperative diagnosis in surgical neuropathology have not changed in the last century, the last several decades have seen dramatic changes in tumor classification, terminology, molecular classification, and modalities used for intraoperative diagnosis. As many neuropathologic intraoperative diagnoses are performed by general surgical pathologists, awareness of these recent changes is important for the most accurate intraoperative diagnosis. To describe recent changes in the practice of intraoperative surgical neuropathology, with an emphasis on new entities, tumor classification, and anticipated ancillary tests, including molecular testing. The sources for this review include the fifth edition of the World Health Organization Classification of Tumours of the Central Nervous System, primary literature on intraoperative diagnosis and newly described tumor entities, and the authors' clinical experience. A significant majority of neuropathologic diagnoses require ancillary testing, including molecular analysis, for appropriate classification. Therefore, the primary goal for any neurosurgical intraoperative diagnosis is the identification of diagnostic tissue and the preservation of the appropriate tissue for molecular testing. The intraoperative pathologist should seek to place a tumor in the most accurate diagnostic category possible, but specific diagnosis at the time of an intraoperative diagnosis is often not possible. Many entities have seen adjustments to grading criteria, including the incorporation of molecular features into grading. Awareness of these changes can help to avoid overgrading or undergrading at the time of intraoperative evaluation.

Peripherin: A proposed biomarker of traumatic axonal injury triggered by mechanical force.

Traumatic axonal injury (TAI) is one of the most common pathological features of severe traumatic brain injury (TBI). Our previous study using proteomics suggested that peripherin (PRPH) should be a potential candidate as a biomarker for TAI diagnosis. This study is to further elucidate the role and association of PRPH with TAI. In the animal study, we performed immunohistochemistry, ELISA and morphological analysis to evaluate PRPH level and distribution following a severe impact. PRPH-positive regions were widely distributed in the axonal tract throughout the whole brain. Axonal injuries with PRPH inclusion were observed post-TBI. Besides, PRPH was significantly increased in both cerebral spinal fluid and plasma at the early phase post-TBI. Colocalization analysis based on microscopy revealed that PRPH represents an immunohistological biomarker in the neuropathological diagnosis of TAI. Brain samples from patients with TBI were included to further test whether PRPH is feasible in the real practice of neuropathology. Immunohistochemistry of PRPH, NFH, APP and NFL on human brain tissues further confirmed PRPH as an immunohistological biomarker that could be applied in practice. Collectively, we conclude that PRPH mirrors the cytoskeleton injury of axons and could represent a neuropathological biomarker for TAI.

The Lundy murders: the role and reliability of forensic neuropathology practice

Mark Lundy was convicted of killing his wife and daughter in 2002 and again in 2015 after a retrial ordered by the Privy Council. His conviction continues to divide public opinion in New Zealand. A key piece of evidence was the presence of small smears on a shirt which prosecution experts identified as central nervous system tissue relying on immunohistochemistry. The successful challenge to his original conviction was part motivated by arguments challenging the reliability of the latter in forensic practice. This has again come under scrutiny following a 2016 report by the US President’s Council of Advisors on Science and Technology. The PCAST concluded that there were two important deficiencies in ensuring scientific validity of so-called ‘feature-comparison methods’. These are procedures by which an examiner seeks to determine whether an evidentiary sample is or is not associated with a source sample based on similar features. Proponents of Lundy’s innocence argue that the application of immunohistochemistry must be regarded as a subjective feature-comparison method. There was a need for (1) clarity about the scientific standards for the validity and reliability of forensic methods and (2) the need to evaluate specific forensic methods to determine whether they have been scientifically established to be valid and reliable. The report emphasised 2 key elements that are required to meet the scientific criteria of foundation validity: (1) a reproducible and consistent procedure and (2) empirical measurements from multiple independent studies of a method’s false positive rate and sensitivity. It is this author’s position that the manner in which the immunohistochemistry was applied in the Lundy case to identify central nervous system tissue was sufficiently robust in terms of rigor and reproducibility and that to insist otherwise would be tantamount to believing in biological alchemy.

P15.08.B Intraoperative confocal laser endomicroscopy of brain tumors - potential and challenges from a neuropathological perspective

Abstract Background Intraoperative consultation, usually in the form of a frozen section, is an integral part of current neuropathology practice. Typical indications include determination of specimen adequacy, intraoperative diagnosis and distinction between tumoral and non-tumoral tissue in diffusely infiltrating gliomas in tumor periphery. The latter is currently limited by the fact that typically not all potential regions of interest can be sampled for frozen sections and the turnaround times of frozen sections usually do not permit multiple repetitive assessments. The commercial availability of a clinical-grade in vivo laser endomicroscope for neurosurgical applications may have the potential to change this and to permit a microscopic analysis in near-real time, which in turn may have a significant impact on resection strategies for brain tumors. In this work, we investigate the potential role of CLE in neurosurgery and the transferability of histological criteria to confocal imaging. Material and Methods The potential role of CLE in neurosurgery in comparison to other techniques for intraoperative tumor assessment was determined by analyzing common intraoperative neuropathological workflows and identifying unaddressed opportunities. The transferability of the histological criteria from standard histology to confocal imaging was achieved by analyzing matched image pairs (standard histology and CLE) from several common tumor entities. Results We identified the time gap between specimen resection and the availability of the frozen section results as an important application for intraoperative CLE imaging in neurosurgery. Importantly, neuropathologists could assess tissue in near real time in an unlimited number of digital biopsies prior to resection, which adds a potent new tool to the neurosurgical armamentarium. CLE images revealed features similar to already known tissue architecture/morphology seen in standard histology, which correlated well in matched histological images. Unique aspects of individual cells and other surrounding tumor tissue elements were observed in vivo while the CLE probe acquired images throughout its focal-depth range. Conclusion Widespread application of CLE may have a major impact on neuropathologists' role in intraoperative diagnosis and bring along both opportunities and challenges. For broad clinical adoption, strategies for histological criteria validation as well as for determination of diagnostic accuracy need to be developed.

Neuropathologic features of central nervous system hemangioblastoma.

Hemangioblastoma is a benign, highly vascularized neoplasm of the central nervous system (CNS). This tumor is associated with loss of function of the VHL gene and demonstrates frequent occurrence in von Hippel-Lindau (VHL) disease. While this entity is designated CNS World Health Organization grade 1, due to its predilection for the cerebellum, brainstem, and spinal cord, it is still an important cause of morbidity and mortality in affected patients. Recognition and accurate diagnosis of hemangioblastoma is essential for the practice of surgical neuropathology. Other CNS neoplasms, including several tumors associated with VHL disease, may present as histologic mimics, making diagnosis challenging. We outline key clinical and radiologic features, pathophysiology, treatment modalities, and prognostic information for hemangioblastoma, and provide a thorough review of the gross, microscopic, immunophenotypic, and molecular features used to guide diagnosis.

Evaluating neurosurgical biopsies for CNS tumor diagnoses: An algorithmic and pattern based approach.

The 2016 and 2021 World Health Organization (WHO) Classifications of Tumors of the Central Nervous System (CNS) reflect the importance of integrating molecular analysis into CNS tumor diagnosis and classification, adding to the complexity of any surgical neuropathology practice. On the other hand, our evolving understanding of genomic alterations across the spectrum of CNS tumors highlights the importance of utilizing traditional histological and immunohistochemical approaches to first establish as accurate a diagnosis as possible. Such an approach is also essential to recognizing the most appropriate ancillary test(s) needed for accurate classification and grading of CNS tumors. Here, we present an algorithmic approach to be considered while evaluating surgical neuropathology biopsies, which includes a recognition of main histological patterns, and incorporates clinical and radiologic features, to assist with accurate diagnosis and optimal selection of subsequent ancillary testing.

Adult Diffuse Astrocytic and Oligodendroglial Tumors.

Infiltrating gliomas comprise the most common group of primary intraparenchymal brain tumors and present a level of complexity which requires careful integration of histopathology and molecular diagnostics for optimal therapy. To this end, the fourth edition of the World Health Organization (WHO) Classification of Tumors of the Central Nervous System (CNS) has been followed by a series of publications by cIMPACT-NOW (the Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy) incorporating molecular signatures to propose updated diagnostic categories in anticipation of the upcoming fifth edition of CNS tumor classification. Integration of histopathology, immunophenotyping, and molecular findings is profoundly changing the practice of diagnostic surgical neuropathology and enabling a more personalized approach to treating patients with gliomas.

Canadian Association of Neuropathologists Association canadienne des neuropathologistes

The Canadian Association of Neuropathologist – Association canadienne des neuropathologistes (CANP-ACNP) held their 60th annual meeting via Zoom from October 15th to 17th, 2020, under the leadership of Dr. Peter Gould, President of the CANP-ACNP, Dr. Peter Schutz, Secretary Treasurer of the CANP-ACNP, and with technical support from CANP administrators Heather Dow and Colleen Fifield.The academic program comprised 10 scientific abstracts, 10 unknown cases, a symposium on Neuromuscular Pathology, and a Neuropathology Practice lecture by Dr. Emina Torlakovic entitled The Fall and Rise of Immunohistochemistry. The interactive forum on Neuropathology Practice was moderated by Dr. Gould and Dr. Keith and focused on forensic neuropathology in Canada. The Jerzy Olszewski Lecture was delivered by Dr. Alex Rajput and Dr. Ali Rajput on Neuropathology and Saskatchewan Movement Disorders Program. Digital pathology images from the 10 unknown cases are available for viewing online (www.canp.ca) thanks to the CANP webmaster Dr. Andrew Gao.The Presidential Symposium 2020 on Neuromuscular Pathology featured the David Robertson Lecture given by Dr. Werner Stenzel entitled The Inflammatory Myopathies – Essential Role of Muscle Biopsies for Precise Diagnosis and the Gordon Mathieson Lecture delivered by Dr. Benjamin Ellezam on The Role of Muscle Biopsy in the Molecular Era: Practical Pointers in Diagnostic Pathology of Inherited Myopathies. The program was completed by Dr. Robert Schmidt’s presentation on Perspectives on the Evaluation of Nerve Biopsies, and Dr. Jodi Warman Chardon’s presentation on MRI & Diagnosis of Muscle Disease.The Mary Tom Award for best clinical science presentation by a trainee went to Dr. Noor Alsafwani (Supervisor Dr. A. Gao), and the Morrison H. Finlayson Award for best basic science presentation by a trainee was won by Dr. Delaney Cosma (Supervisor Dr. R. Hammond).The following abstracts were presented at the 60th annual meeting of the Canadian Association of Neuropathologists – Association candienne des neuropathologistes (CANP-ACNP) in October 2020.

Molecular Diagnostics of Adult Gliomas in Neuropathological Practice.

This review focuses on adult gliomas, highlighting the most relevant biomarkers in the diagnosis of these tumours and the use of DNA methylation arrays to complement conventional molecular diagnostic techniques. The discovery and characterisation of diagnostic and prognostic biomarkers in brain tumours has significantly changed the neuropathological landscape over the last decade. These include mutations in the IDH1 and IDH2 genes in astrocytomas and oligodendrogliomas, histone H3 K27M mutations in midline gliomas, or BRAF mutations in a range of low-grade and high-grade glial and glioneuronal tumours. Other biomarkers of relevance are mutations in the TERT promoter, the ATRX gene, and genomic alterations such as 1p/19q codeletion, EGFR amplification, and chromosome 7 gain and 10 loss. The development of DNA methylation profiling and algorithmic classification of brain tumours has further enhanced the diagnostic abilities of neuropathologists. Methylation profiling is particularly useful for the diagnostic workup of biopsies with an inconclusive molecular test results, small samples, or samples with indistinctive low-grade or high-grade histology. This technology has become indispensable for the risk stratification of ependymal tumours, medulloblastomas and meningiomas. CONCLUSION: This review highlights the importance of an integrated approach to brain tumour diagnostics and gives a balanced view of the relevance and choice of conventional and molecular techniques in the workup of adult gliomas in diagnostic neuropathology practice.

Canadian Association of Neuropathologists L’Association Canadienne des Neuropathologistes

The Canadian Association of Neuropathologist – L’ Association Canadienne de Neuropathologistes (CANP-ACNP) held their 59th annual meeting at the Delta Kingston Waterfront from October 23rd to 26th, 2019, under the leadership of Dr. Peter Gould, President of the CANP-ACNP, Dr. Julia Keith, Secretary Treasurer of the CANP-ACNP, and Dr. John Rossiter, local organizer. The annual banquet was held at River Mill Restaurant in Kingston.The academic program comprised 14 Abstracts, 14 unknown cases, a Symposium on Neurodegenerative Neuropathology, and a Neuropathology Practice lecture by Dr. Gerard Jansen entitled CJD, CJD Surveillance, and Occupational Risk. Can worms ever be re-canned? The interactive forum on Neuropathology Practice was moderated by Dr. Gould and Dr. Keith and focused on safety around autopsy diagnosis of CJD, the Neuropathology workforce analysis in Canada 2019 presented by Dr. Patrick Shannon, and accreditation of neuropathology laboratories in Canada. Digital pathology images from the 14 unknown cases are available for viewing online (www.canp.ca) thanks to the CANP webmaster Dr. Jason Karamchandani.The Presidential Symposium 2019 on Neurodegenerative Neuropathology featured the Jerry Olszewski Lecture given by Dr. Douglas Munoz on Using eye tracking to identify behavioural biomarkers of neurodegeneration, the David Robertson lecture given by Dr. Tom Beach on Staging systems for Lewy body diseases, and the Gordon Mathieson lecture given by Dr. Ian Mackenzie on C9orf72: FTD, ALS and beyond. The program was completed Dr. Gabor Kovacs’ presentation on Tau pathologies in the aging brain and Dr. Carmela Tartaglia’s presentation on Dementia; the times they are a changing.The award for best clinical science presentation by a trainee (Dr. Mary Tom Award) in 2019 went to Dr. Suzy Kosteniuk (Supervisor Dr. Lothar Resch), and the award for best basic science presentation by a trainee (Dr. Morrison H. Finlayson Award) was won by Hoang D. Nguyen (Supervisor Dr. Maxime Richer).The following abstracts were presented at the 59th annual meeting of the Canadian Association of Neuropathologists – Association Candienne des Neuropathologistes (CANP-ACNP) in October 2019.

Multipolar Neuropathology: Survival Strategies for Professional Loneliness

Abstract The field of neuropathology has a rich history with strong ties to the clinical fields of neurosurgery and neurology. Until the mid-20th century, neuropathology was an apprenticeship in these fields after which it became a subspecialty within the field of pathology. Neuropathology remains a small subspecialty, encompassing only 2% of the actively practicing pathologists in the United States, which lends to the professional loneliness that may occur with neuropathologists. This review offers a guide that covers the most important aspects of a neuropathology practice, including the use of telepathology in a neuropathology practice, the most important aspects of intraoperative evaluation of surgical neuropathology specimens, fellowship training, and the role of neuropathologists in forensic pathology.

Rapid Validation of Telepathology by an Academic Neuropathology Practice During the COVID-19 Pandemic.

The coronavirus disease 19 (COVID-19) pandemic is placing unparalleled burdens on regional and institutional resources in medical facilities across the globe. This disruption is causing unprecedented downstream effects to traditionally established channels of patient care delivery, including those of essential anatomic pathology services. With Washington state being the initial North American COVID-19 epicenter, the University of Washington in Seattle has been at the forefront of conceptualizing and implementing innovative solutions in order to provide uninterrupted quality patient care amidst this growing crisis. To conduct a rapid validation study assessing our ability to reliably provide diagnostic neuropathology services via a whole slide imaging (WSI) platform as part of our departmental COVID-19 planning response. This retrospective study assessed diagnostic concordance of neuropathologic diagnoses rendered via WSI as compared to those originally established via traditional histopathology in a cohort of 30 cases encompassing a broad range of neurosurgical and neuromuscular entities. This study included the digitalization of 93 slide preparations, which were independently examined by groups of board-certified neuropathologists and neuropathology fellows. There were no major or minor diagnostic discrepancies identified in either the attending neuropathologist or neuropathology trainee groups for either the neurosurgical or neuromuscular case cohorts. Our study demonstrates that accuracy of neuropathologic diagnoses and interpretation of ancillary preparations via WSI are not inferior to those generated via traditional microscopy. This study provides a framework for rapid subspecialty validation and deployment of WSI for diagnostic purposes during a pandemic event.

What Every Neuropathologist Needs to Know: The Muscle Biopsy.

Competence in muscle biopsy evaluation is a core component of neuropathology practice. The practicing neuropathologist should be able to prepare frozen sections of muscle biopsies with minimal artifacts and identify key histopathologic features of neuromuscular disease in hematoxylin and eosin-stained sections as well as implement and interpret a basic panel of additional histochemical, enzyme histochemical, and immunohistochemical stains. Important to everyday practice is a working knowledge of normal muscle histology at different ages, muscle motor units, pitfalls of myotendinous junctions, nonpathologic variations encountered at traditional and nontraditional muscle sites, the pathophysiology of myonecrosis and regeneration, and approaches to distinguish muscular dystrophies from inflammatory myopathies and other necrotizing myopathies. Here, we provide a brief overview of what every neuropathologist needs to know concerning the muscle biopsy.

Validation of machine learning models to detect amyloid pathologies across institutions

Semi-quantitative scoring schemes like the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) are the most commonly used method in Alzheimer’s disease (AD) neuropathology practice. Computational approaches based on machine learning have recently generated quantitative scores for whole slide images (WSIs) that are highly correlated with human derived semi-quantitative scores, such as those of CERAD, for Alzheimer’s disease pathology. However, the robustness of such models have yet to be tested in different cohorts. To validate previously published machine learning algorithms using convolutional neural networks (CNNs) and determine if pathological heterogeneity may alter algorithm derived measures, 40 cases from the Goizueta Emory Alzheimer’s Disease Center brain bank displaying an array of pathological diagnoses (including AD with and without Lewy body disease (LBD), and / or TDP-43-positive inclusions) and levels of Aβ pathologies were evaluated. Furthermore, to provide deeper phenotyping, amyloid burden in gray matter vs whole tissue were compared, and quantitative CNN scores for both correlated significantly to CERAD-like scores. Quantitative scores also show clear stratification based on AD pathologies with or without additional diagnoses (including LBD and TDP-43 inclusions) vs cases with no significant neurodegeneration (control cases) as well as NIA Reagan scoring criteria. Specifically, the concomitant diagnosis group of AD + TDP-43 showed significantly greater CNN-score for cored plaques than the AD group. Finally, we report that whole tissue computational scores correlate better with CERAD-like categories than focusing on computational scores from a field of view with densest pathology, which is the standard of practice in neuropathological assessment per CERAD guidelines. Together these findings validate and expand CNN models to be robust to cohort variations and provide additional proof-of-concept for future studies to incorporate machine learning algorithms into neuropathological practice.