A Pilot Validation Study Comparing Fluorescence-Imitating Brightfield Imaging, A Slide-Free Imaging Method, With Standard Formalin-Fixed, Paraffin-Embedded Hematoxylin-Eosin-Stained Tissue Section Histology for Primary Surgical Pathology Diagnosis

CONTEXT.—

Digital pathology using whole slide images has been recently approved to support primary diagnosis in clinical surgical pathology practices. Here we describe a novel imaging method, fluorescence-imitating brightfield imaging, that can capture the surface of fresh tissue without requiring prior fixation, paraffin embedding, tissue sectioning, or staining.

OBJECTIVE.—

To compare the ability of pathologists to evaluate direct-to-digital images with standard pathology preparations.

DESIGN.—

One hundred surgical pathology samples were obtained. Samples were first digitally imaged, then processed for standard histologic examination on 4-μm hematoxylin-eosin-stained sections and digitally scanned. The resulting digital images from both digital and standard scan sets were viewed by each of 4 reading pathologists. The data set consisted of 100 reference diagnoses and 800 study pathologist reads. Each study read was compared to the reference diagnosis, and also compared to that reader's diagnosis across both modalities.

RESULTS.—

The overall agreement rate, across 800 reads, was 97.9%. This consisted of 400 digital reads at 97.0% versus reference and 400 standard reads versus reference at 98.8%. Minor discordances (defined as alternative diagnoses without clinical treatment or outcome implications) were 6.1% overall, 7.2% for digital, and 5.0% for standard.

CONCLUSIONS.—

Pathologists can provide accurate diagnoses from fluorescence-imitating brightfield imaging slide-free images. Concordance and discordance rates are similar to published rates for comparisons of whole slide imaging to standard light microscopy of glass slides for primary diagnosis. It may be possible, therefore, to develop a slide-free, nondestructive approach for primary pathology diagnosis.

Neuropathological Applications of Microscopy with Ultraviolet Surface Excitation (MUSE): A Concordance Study of Human Primary and Metastatic Brain Tumors

Whereas traditional histology and light microscopy require multiple steps of formalin fixation, paraffin embedding, and sectioning to generate images for pathologic diagnosis, Microscopy using Ultraviolet Surface Excitation (MUSE) operates through UV excitation on the cut surface of tissue, generating images of high resolution without the need to fix or section tissue and allowing for potential use for downstream molecular tests. Here, we present the first study of the use and suitability of MUSE microscopy for neuropathological samples. MUSE images were generated from surgical biopsy samples of primary and metastatic brain tumor biopsy samples (n = 27), and blinded assessments of diagnoses, tumor grades, and cellular features were compared to corresponding hematoxylin and eosin (H&E) images. A set of MUSE-treated samples subsequently underwent exome and targeted sequencing, and quality metrics were compared to those from fresh frozen specimens. Diagnostic accuracy was relatively high, and DNA and RNA integrity appeared to be preserved for this cohort. This suggests that MUSE may be a reliable method of generating high-quality diagnostic-grade histologic images for neuropathology on a rapid and sample-sparing basis and for subsequent molecular analysis of DNA and RNA.

Utility of fluorescence imitating brightfield imaging microscopy for the diagnosis of feline chronic enteropathy

Fluorescence imitating brightfield imaging (FIBI) is a novel microscopy method that allows for real-time, nondestructive, slide-free tissue imaging of fresh, formalin-fixed, or paraffin-embedded tissue. The nondestructive nature of the technology permits tissue preservation for downstream analyses. The objective of this observational study was to assess the utility of FIBI compared with conventional hematoxylin and eosin (H&E)-stained histology slides in feline gastrointestinal histopathology. Formalin-fixed paraffin-embedded full-thickness small intestinal tissue specimens from 50 cases of feline chronic enteropathy were evaluated. The ability of FIBI to evaluate predetermined morphological features (epithelium, villi, crypts, lacteals, fibrosis, submucosa, and muscularis propria) and inflammatory cells was assessed on a 3-point scale (0 = FIBI cannot identify the feature; 1 = FIBI can identify the feature; 2 = FIBI can identify the feature with more certainty than H&E). H&E and FIBI images were also scored according to World Small Animal Veterinary Association (WSAVA) Gastrointestinal Standardization Group guidelines. FIBI identified morphological features with similar or, in some cases, higher confidence compared with H&E images. The identification of inflammatory cells was less consistent. FIBI and H&E images showed an overall poor agreement with regard to the assigned WSAVA scores. While FIBI showed an equal or better ability to identify morphological features in intestinal biopsies, its ability to identify inflammatory cells is currently inferior compared with H&E-based imaging. Future studies on the utility of FIBI as a diagnostic tool for noninflammatory histopathologic lesions are warranted.

TAMI-77. CHARACTERIZATION OF METABOLIC DIFFERENCES IN MENINGIOMAS USING TUMOR TISSUE AND PATIENT-DERIVED CELL LINES

As more information emerges on metabolic changes in brain pathologies, mass spectrometry methodologies are needed to investigate cellular changes in primary brain tumors. Many approaches use technologies that lack sensitivity and selectivity, which hinders discovering potential novel diagnostic and prognostic features. Fresh frozen tissue from 26 patients (57% women, 43% men, age 21-67) underwent surgical resection for newly diagnosed meningiomas. We used patient-derived cell lines and arachnoid cells to validate and compare metabolic differences in patient tumor tissue. Primary metabolism (GC-TOF), lipidomics, and biogenic amines (RPLC and HILIC-HRMS) were analyzed using 10 mg of tissue and 1x106 cells. RESULTS: Primary metabolism and lipidomics showed significant differences between Grade I and Grade II tumors. We identified over one thousand total metabolites through authentic standards and MS2 fragmentation patterns. Ascorbic Acid was enriched in Grade I tumors compared to Grade II and enriched in tumors compared to non-neoplastic dura tissue from the same patient. Lysosomal activation in atypical meningiomas is indicated by a 2-fold increase (compared to Grade I tumors) of Bis(monoacylglycero)phosphate metabolites. We grouped metabolites into fifteen classes based on chemical ontology and function. Statistically significant differences were observed in total amino acids (AA), basic AA, cyclic AA, sulfur-containing AA, branched-chain AA, dipeptides, histidine-containing dipeptides, vitamins and cofactors, glutathione metabolites, acylcarnitine’s, sphingomyelins, phosphatidylethanolamines, phosphatidylinositol’s, cardiolipins, and nucleic acids. Thymine-containing nucleic acids and biogenic monoamines were 2-fold higher in Grade I compared to Grade II tumors. Using novel untargeted metabolomics, we found multiple classes of metabolites that were enriched in Grade II meningiomas compared to Grade I. This points towards possible pathways that drive malignancy and biomarkers that could be useful for diagnosis, grading, and treatment selection.

Exposure to DMSO during infancy alters neurochemistry, social interactions, and brain morphology in long-evans rats

INTRODUCTION

Dimethyl sulfoxide (DMSO) is a widely used solvent to dissolve hydrophobic substances for clinical uses and experimental in vivo purposes. While usually regarded safe, our prior studies suggest changes to behavior following DMSO exposure. We therefore evaluated the effects of a five-day, short-term exposure to DMSO on postnatal infant rats (P6-10).

METHODS

DMSO was intraperitoneally injected for five days at 0.2, 2.0, and 4.0 ml/kg body mass. One cohort of animals was sacrificed 24 hr after DMSO exposure to analyze the neurometabolic changes in four brain regions (cortex, hippocampus, basal ganglia, and cerebellum) by hydrophilic interaction liquid chromatography. A second cohort of animals was used to analyze chronic alterations to behavior and pathological changes to glia and neuronal cells later in life (P21-P40).

RESULTS

164 metabolites, including key regulatory molecules (retinoic acid, orotic acid, adrenic acid, and hypotaurine), were found significantly altered by DMSO exposure in at least one of the brain regions at P11 (p < .05). Behavioral tests showed significant hypoactive behavior and decreased social habits to the 2.0 and 4.0 ml DMSO/kg groups (p < .01). Significant increases in number of microglia and astrocytes at P40 were observed in the 4.0 ml DMSO/kg group (at p < .015.) CONCLUSIONS: Despite short-term exposure at low, putatively nontoxic concentrations, DMSO led to changes in behavior and social preferences, chronic alterations in glial cells, and changes in essential regulatory brain metabolites. The chronic neurological effects of DMSO exposure reported here raise concerns about its neurotoxicity and consequent safety in human medical applications and clinical trials.

TAMI-60. EXPLORING METABOLIC DIFFERENCES IN VARYING GRADES OF MENINGIOMAS THROUGH NONTARGETED MASS SPECTROMETRY

Emerging molecular data demonstrates the importance of genomic and epigenetic factors in pathogenesis of meningioma. Understanding the metabolic landscape using mass spectrometry is needed to overcome significant uncertainty in predicting tumor behavior and the risk of recurrence. Current technologies lack sensitivity and selectivity, which hinders the discovery of potential novel diagnostic and prognostic features. Here, we present a nontargeted metabolomics approach applied to meningiomas for biomarker discovery and identification of potential therapeutic targets. Fresh frozen tissue from 36 patients (57% women, 43% men; mean age: 48) who underwent surgical resection for newly diagnosed meningiomas and 9 patient samples with non-neoplastic dura were used for case/control comparison. Additionally, 16 patient-derived meningioma cell lines (Grade I-III), 2 immortalized human cell lines (IOMM-Lee and Ch157MN) and immortalized arachnoid cells were used to further explore metabolic changes in meningiomas. Metabolites were extracted from tissue and cells for GC-TOF (primary metabolism), RPLC ESI (±) (lipidomics) and HILIC ESI (±) (biogenic amines) coupled to high-resolution mass spectrometry for analysis. Metabolites were identified using authentic standards, retention time, and MS2 fragmentation. Over one thousand known metabolites were identified and annotated as well as over 300 unknown metabolites. Metabolites were grouped into one of fifteen classes based on chemical ontology and function. Bis(monoacylglycero)phosphates were over 2-fold increase in atypical (Grade II) meningiomas versus Grade I, indicating lysosomal activation. One carbon metabolism pathway showed significant upregulation in neoplastic tissue vs. tumor involved dura, as well as neoplastic cells compared to arachnoid cells, indicating folate-dependent pathways as a potential therapeutic target. Using novel combined untargeted metabolomics, we found multiple classes of metabolites that were either enriched or suppressed in neoplastic tissue and cells compared to non-neoplastic cells. Further studies are warranted for a better understanding of possible oncogenic signaling pathways and to detect potential biomarkers useful for diagnosis and treatment.