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.

We examined recurrence after gross total resection (GTR) or subtotal resection (STR) at St. Michael’s Hospital, Toronto, of 181 cases of atypical meningioma (WHO grade II). In the entire group, Kaplan-Meier survival curves showed that combined necrosis and brain invasion was the feature associated with the worst outcome, followed in order by necrosis, histological variants (clear cell, rhabdoid, and chordoid), high mitotic count, and brain invasion. The highly significant difference between necrosis and brain invasion and necrosis was seen only in patients receiving GTR, and lost in those treated with STR. Adjuvant radiotherapy was associated with worse outcome, more so in patients receiving GTR. In the presence of high mitotic count (defined as >4/10HPF) radiation did not affect recurrence, but necrosis and specially combined necrosis and brain invasion magnified the apparent deleterious effect of adjuvant radiotherapy. In the presence of brain invasion, radiotherapy’s small effect did not reach significance. Since patients were not randomized to adjuvant radiotherapy, these results should not be construed as indicating that this treatment is injurious. It can be stated that in the presence of necrosis and particularly necrosis and brain invasion, but not brain invasion alone, or high mitotic count, atypical meningiomas are more resistant to any possible beneficial effect of radiation in delaying recurrence.

Classification of primary CNS tumours is currently achieved by complementing histologic analysis with molecular information, in accordance with the WHO guidelines, and aims at providing accurate prognosis and optimal patient management. cIMPACT-NOW update 3 now recommends grading diffuse IDH-wild type astrocytomas as grade IV glioblastomas if they bear one or more of the following molecular alterations: EGFR amplification, TERT promoter mutation, and whole-chromosome 7 gain combined with chromosome 10 loss. In this reanalysis of the Cancer Genome Atlas (TCGA) glioma expression datasets, we identified 14 IDH-wt infiltrating astrocytic gliomas displaying a “normal-like (NL)” transcriptomic profile associated with a longer survival rate. Some of these tumours would be considered as GBM-equivalents with the current diagnostic algorithm. A k-nearest neighbors model was used to identify 3-gene signatures able to identify NL IDH-WT gliomas. Genes such as C5AR1 (complement receptor) SLC32A1 (vesicular gamma-aminobutyric acid transporter), and SMIM10L2A (long non-coding RNA) were overrepresented in these signatures which were validated further using the Chinese Glioma Genome and Ivy Glioblastoma Atlases. They showed high discriminative power and correlation with survival. This finding could lead to the validation of an immunohistochemical or PCR test which would facilitate classification of IDH-WT astrocytomas with unclear histological grading. Furthermore, associated signaling pathways might represent novel treatment targets for aggressive tumours.

Flow cytometry of the cerebrospinal fluid (CSF) is used in isolation or as an adjunct to cytology to increase the sensitivity of detecting primary central nervous system (CNS) lymphoma. We aim to evaluate the sensitivity of CSF flow cytometry as a diagnostic tool for primary CNS lymphoma in patients presenting with undifferentiated neurologic symptoms. We retrospectively reviewed all CSF samples received by the Calgary Laboratory Services Flow Cytometry Laboratory from 2012- 2015. Clinical data, laboratory investigations, radiologic imaging studies, and pathological data were analyzed. Clinical review extended to 2 years post CSF flow cytometric testing. The number of samples of CSF flow cytometry that were positive for a hematological malignancy was 43/763 (5.6%). The overall sensitivity of the test was 69.4%. A positive result was more likely to occur in patients with a prior history of a hematological malignancy or abnormal enhancement on MRI (p<0.0001). CSF flow cytometry was negative in all patients who did not have a previous hematological malignancy or abnormal enhancement on MRI (n = 247). CSF flow cytometry has a limited role in screening for primary CNS lymphoma, unless a strictly endorsed testing algorithm is applied. It is, however, an invaluable tool in evaluating CNS involvement in patients with a previous diagnosis of hematolymphoid malignancy or abnormal enhancement on MRI.

Calcifying pseudoneoplasm of the neuraxis (CAPNON) is a rare tumefactive lesion with unclear pathogenesis. It is diagnosed by pathological findings of the typical histological features that include granular amorphous cores with palisading spindle to epithelioid cells, variable fibrous stroma, foreign-body reaction with giant cells, and calcification/ossification occasionally with psammoma bodies. However, its histopathology may be variable and currently immunohistochemistry plays a limited role in its diagnosis and understanding the pathogenesis. In this study, we examined 6 cases of CAPNONs including 3 intracranial and 3 spinal epidural lesions (age range: 59–69 years; 3 males and 3 females). Immunohistochemistry revealed that all CAPNON cores contain abundant positive deposits of neurofilament protein (NFP), which was supported by electron microscopy finding of filaments (8–13 nm in diameter). In comparison, no NFP positivity was found in 5 psammomatous/metaplastic meningiomas or 7 intervertebral tissue lesions with calcification/ossification. In addition, CAPNON cellular areas showed variable numbers of CD8+ cytotoxic T-cells with less CD4+ T-cells and a decreased ratio of CD4/CD8+ cells, versus the intervertebral tissue lesions without CD8+ or CD4+ cells. Our findings suggest that NFP may be a principal constituent of CAPNONs, and thus involved in the pathogenesis of CAPNON. Given the decreased CD4/CD8 ratio, the pathogenic process of CAPNON is possibly immune- mediated.

Deep learning, a subset of artificial intelligence, has shown great potential in several recent applications to pathology. These have mainly involved the use of classifiers to diagnose disease, while generative modelling techniques have been less frequently used. Generative adversarial networks (GANs) are a type of deep learning model that has been used to synthesize realistic images in a range of domains, both general purpose and medical. In the GAN framework, a generator network is trained to synthesize fake images, while a dueling discriminator network aims to distinguish between the fake images and a set of real training images. As GAN training progresses, the generator network ideally learns the important features of a dataset, allowing it to create images that the discriminator cannot distinguish from the real ones. We report on our use of GANs to synthesize high resolution, realistic histopathology images of gliomas. The well- known Progressive GAN framework was trained on a set of image patches extracted from digital slides in the Cancer Genome Atlas repository, and was able to generate fake images that were visually indistinguishable from the real training images. Generative modelling in pathology has numerous potential applications, including dataset augmentation for training deep learning classifiers, image processing, and expanding educational material.

Alexander Disease (AD) is a rare and ultimately lethal leukodystrophy, typically presenting in infants who exhibit developmental delay, macrocephaly, seizures, spasticity and quadriparesis. Classic infantile forms are generally due to sporadic mutations in GFAP that result in the massive deposition of intra-astrocytic Rosenthal fibres, particularly in the frontal white matter. However, phenotypic manifestations are broad and include both juvenile and adult forms that often display infratentorial pathology and a paucity of leukodystrophic features. We describe the unique case of an 8.5 year old female who presented with an 8 month history of progressively worsening vomiting and cachexia, whose extensive multidisciplinary systemic workup, including GI biopsies, proved negative. Neuroimaging ultimately revealed bilaterally symmetric and anterior predominant supratentorial signal alterations in the white matter plus a 1.7 x 1.2 x 0.7 mm right dorsal medullary mass. Biopsy of this presumed low-grade glioma revealed features in keeping with AD, which was later confirmed on whole exome sequencing. The proband exhibited a pathogenic p.Arg239Cys heterozygous missense mutation in GFAP, which was apparently inherited from her asymptomatic mother (1% mosaicism in the mother’s blood). Germline mosaic inheritance patterns of young-onset AD, particularly those presenting with a tumor-like mass of the brainstem, are scarcely reported in the literature and serve to expand the clinicopathologic spectrum of AD.

Neuroaxonal Dystrophies (NAD) are neurodegenerative diseases characterized by axonal “spheroids” occurring in different age groups. The identification of mutations delineated new molecular entities in these disorders. We report neuropathological data of a new form of NAD, characterized by a precocious prenatal onset, different from classical and conatal Infantile Neuroaxonal Dystrophy (INAD).

We studied 5 fetuses examined after pregnancy termination and 2 term neonates deceased just after birth, 4/7 born from consanguineous parents. All subjects presented severe fetal akinesia sequence with microcephaly. In 4/7 cases, a molecular study was performed. In all cases, “spheroids” with typical immunohistochemical features were identified, with variable spreading in the central and peripheral nervous system. Basal ganglia, brainstem, cerebellum, and spinal cord involvement was constant. Associated CNS malformations, unusual in INAD, were associated including hydrocephalus (2), callosal agenesis/hypoplasia (2), olfactory agenesis (1), cortical (3) and retinal (1) anomalies. None of the cases demonstrated mutations in PLA2G6, found in INAD. The clinical and neuropathological features of these fetal cases are different from those of “classical” INAD. The absence of mutations in PLA2G6, in addition, suggests that the fetal NAD is a new entity, distinct from INAD, with different molecular basis. Associated malformations suggest a wide phenotypic spectrum and probable genetic heterogeneity. Finally, fetal NAD is an additional etiology of fetal akinesia.

A 31-year-old female hairdresser whose parents were first degree cousins complained of episodic attacks of headache, vomiting, and dizziness for the past eight years after an uneventful childhood and adolescence. Four years ago, she developed progressive weakness, muscle pain and difficulties walking and lifting her arms that she could not work in her profession anymore. She lost hair, weight and became amenorrhoic. Finally, her muscle weakness required intensive care. Early on her CK was mildly elevated to 237 U/l (normal < 167), but later to 900 and 1800. By MRI, skeletal muscles showed minimal contrast enhancement.

The clinically suspected diagnosis of myositis prompted repeated muscle biopsies, which disclosed non-specific myopathic changes, scattered necrotic muscle fibers without inflammation, protein aggregation, or vacuolation by light microscopy, but abnormally structured mitochondria with inclusions by electron microscopy, and treatment with steroids without any clinical improvement.

A panel of 1131 mitochondrial genes revealed a homozygous mutation in the ETFDH gene.

Chronic traumatic encephalopathy (CTE) and aging-related tau astrogliopathy (ARTAG) are characterised by tau-immunopositive neuronal and/or astrocytic inclusions, with overlapping cortical involvement and astrocytic inclusion morphology. This study determined the prevalence of CTE and cortical ARTAG in a European community-based population (n=310) and explored overlap of both pathological entities. Frontal, parietal and temporal cortices were assessed. No case fulfilling CTE criteria was found. However, isolated astroglial or neuronal tau pathologies were recognized in sulcal depths (<2%). One case without history of traumatic brain injury showed combined tau-immunoreactive features confined to frontal sulci without perivascular accumulation. Another 24 cases had single tau pathologies in cortical sulci. ARTAG was identified in 117 cases (38%), with a similar regional prevalence. Grey matter ARTAG was the most common followed by subpial, white matter and perivascular. The presence of any type of ARTAG was associated with having another type of ARTAG in the same region (P<0.05). In summary, cortical ARTAG in this population is common and contrasts the high prevalence of CTE in individuals with repeated mild traumatic brain injury.

Nodding syndrome (NS) is an enigmatic recurrent epidemic neurological disease that affects children in East Africa. The illness begins with nodding of the head and grand mal seizures that may lead to death after several years. The most recent outbreaks of NS occurred in northern Uganda and South Sudan. We describe the clinicopathologic spectrum of NS in Uganda. Ten children or young adults with NS were studied at autopsy and the neuropathological findings correlated with the onset, duration and progression of their neurological illness. All cases had epilepsy with grand mal seizures. Three cases had a clinical course that was predominantly characterized by epilepsy. Seven patients had progressive frontotemporal dementia. Two of the patients with dementia also had progressive quadriparesis. In all cases, the brain revealed tau pathology. In cases with an epilepsy-predominate course, the tau pathology was largely limited to the anterior frontal lobes but cases with dementia had more widespread cortical and subcortical tau pathology. In some cases, the histologic pattern was reminiscent of progressive supranuclear palsy. There are some interesting parallels between NS and the amyotrophic lateral sclerosis/Parkinson-dementia complex (ALS/PDC). The similarities are the presence of geographical isolates of disease manifesting in indigenous populations with familial clusters but no clear heritability. Both disorders appear to be related to an unknown environmental factor and both diseases appear to be fading over time in the respective geographical locations. One of the major open questions is whether ALS occurs in NS. This question will be addressed in future clinical studies and postmortem examination of the spinal cord. We propose that NS is a unique epilepsy-dementia complex in East Africa.

The amygdala is a key anatomic structure that has multiple different nuclei and is involved in several critical aspects of cognition and systemic functions. Several different neurodegenerative diseases have major pathological effects on distinct amygdala nuclei. This presentation will describe the classic and characteristic anatomic distributions in the amygdala of “pure” Alzheimer disease and “pure” Lewy body disease, as well as “normal aging”. In addition, data will be presented on how these classic distributions are altered in either “mixed dementias” or in some atypical forms of neurodegeneration. Amygdala pathology will also be illustrated in several other neurodegenerative diseases. The implications of the differing anatomic distributions in different neurodegenerative diseases will be discussed.

Dorsal root ganglia (DRG) at all levels of the spinal cord are a prominent target of Friedreich ataxia (FA). The lesions include hypoplasia of neurons, proliferation of satellite cells, infiltration by IBA- 1-reactive monocytes, and formation of residual nodules. Paucity and smallness of DRG neurons account for the lack of large myelinated axons in dorsal roots and sensory peripheral nerves. The lack of myelin in dorsal roots can be attributed to low levels of neuregulin 1 type III (NRG1[III]). Lysates of 13 DRG of genetically confirmed FA patients were analyzed by antibody microarray with 878 different validated antibodies that target structural and signaling proteins, and by Western blots. KIT and mTOR, two proteins involved in cellular proliferation, were significantly upregulated in the DRG of FA. KIT is a transmembrane receptor that dimerizes when it binds two molecules of stem cell factor (SCF) in its extracellular domain and becomes activated as protein tyrosine kinase. Immunohistochemistry with anti-KIT generated reaction product in satellite cells of normal DRG and prominent labeling of these cells in FA that co-localized with SCF on double- label immunofluorescence; SCF was present in S100-positive satellite cells rather than monocytes. Immunohistochemical reaction product of mTOR and other mTOR complex proteins, such as hamartin (TSC1), tuberin (TSC2), raptor (mTOR complex 1) and rictor (mTOR complex 2) was also present in satellite cells of normal DRG and DRG of FA. Antibodies to two downstream proteins that are considered to be indicators of mTOR activity, P70 S6K and 4E-binding protein 1, revealed no reaction product in DRG of FA. TSC1, TSC2, and mTOR are best known from their roles in tuberous sclerosis, but expression of these proteins, and KIT, in DRG may contribute to signaling cascades underlying the proliferation of satellite cells in FA.

To characterize the professional occupation of Canadian neuropathologists and estimate the future employment demands in neuropathologists, all the active members of the Canadian Association of Neuropathologists in Canada (n=53) were surveyed by E-mail, inquiring as to their estimated date of retirement, their current employment and practice profile, and as to any practice trends they had noticed. 49 members replied: all but one practice at medical school centers. 38 practice exclusively in neuropathology and three of these are employed at less than 75% of a full time equivalent. The remaining practices are mixed neuropathology and anatomical pathology, and one practices exclusively ophthalmic pathology. 35% reported significant neuropathology sub specialization (e.g. forensic, pediatric, neuromuscular). 42% reported greater than 10% of time dedicated to research (of these, median 30%) and 35% greater than 10% time spent in teaching, and 9% greater than 10% time in administration. Of the 49 surveyed, as of the spring of 2019, 14%(seven) of the full time neuropathologists can be expected to retire in the next 10 years, and 6% (three) with mixed AP/NP practices.