Challenging pitfalls in frozen section pathology: a case of mandible ghost cell odontogenic carcinoma and the literature review.

BACKGROUND: Ghost cell odontogenic carcinoma (GCOC) is a rare malignancy characterized by the presence of ghost cells, preferably in the maxilla. Only slightly more than 50 case reports of GCOC have been documented to date. Due to the rarity of this tumor and its nonspecific clinical criteria, there is a heightened risk of misdiagnosis in clinical examination, imaging findings, and pathology interpretation. CASE PRESENTATION: A 50-year-old male patient presented to the hospital due to experiencing pain in his lower front teeth while eating for the past 2 months. Upon examination, a red, hard, painless mass was found in his left lower jaw, measuring approximately 4.0 cm × 3.5 cm. Based on the malignant histological morphology of the tumor and the abundant red-stained keratinized material, the preoperative frozen section pathology misdiagnosed it as squamous cell carcinoma (SCC). The surgical resection specimen pathology via paraffin section revealed that the tumor was characterized by round-like epithelial islands within the fibrous interstitium, accompanied by a large number of ghost cells and some dysplastic dentin with infiltrative growth. The malignant components displayed marked heterogeneity and mitotic activity. Additionally, a calcified cystic tumor component of odontogenic origin was observed. Hemorrhage, necrosis, and calcifications were present, with a foreign body reaction around ghost cells. Immunoreactivity for ß-catenin showed strong nuclear positivity in tumor cells, while immunostaining was completely negative for p53. The Ki67 proliferation index was approximately 30-40%. The tumor cells exhibited diffuse CK5/6, p63, and p40 immunoreactivity, with varying immunopositivity for EMA. Furthermore, no BRAFV600E mutation was identified by ARMS-PCR. The final pathology confirmed that the tumor was a mandible GCOC. CONCLUSION: We have reported and summarized for the first time the specific manifestations of GCOC in frozen section pathology and possible pitfalls in misdiagnosis. We also reviewed and summarized the etiology, pathological features, molecular characteristics, differential diagnosis, imaging features, and current main treatment options for GCOC. Due to its rarity, the diagnosis and treatment of this disease still face certain challenges. A correct understanding of the pathological morphology of GCOC, distinguishing the ghost cells and the secondary stromal reaction around them, is crucial for reducing misdiagnosis rates.

[Fluorescence confocal microscopy-complete digitization of pathology]. / Fluoreszenzbasierte Konfokalmikroskopie ­ vollständige Digitalisierung der Pathologie.

BACKGROUND: Fluorescence-based confocal microscopy (FCM) can be used to create virtual H&E sections in real time. So far, FCM has been used in dermato-, uro-, and gynecopathology. FCM allows the creation of a completely digitized frozen section, which could potentially replace conventional frozen sections in the future. OBJECTIVE: The aim of the current work is to implement FCM technology as a component of fully digitized processes in the pathological workflow. For this purpose, the current use of FCM in liver transplant pathology will be extended to other disciplines such as urology and otorhinolaryngology. MATERIALS AND METHODS: The FCM technique continues to be used prospectively on native tissue samples from potential donor livers. Conventional frozen sections are used comparatively to virtual FCM scans. RESULTS: The data show a nearly perfect agreement for the detection of cholangitis, fibrosis, and malignancy, and a high level of agreement for, e.g., macrovesicular steatosis, inflammation, steatohepatitis, and necrosis between virtual FCM scans and conventional routine diagnostic frozen sections. CONCLUSION: Since the availability of time- and cost-intensive frozen section diagnostics in the context of transplant pathology in continuous operation (24/7) is now only established at very few university centers in Germany due to an increasing shortage of specialists, the use of FCM could be an important building block in the current process leading towards a fully digitized pathology workflow and should thus be extended to various disciplines.

Using Initial Biopsies and Vertical Sections to Improve Trainees' Confidence in Performing Mohs Surgery.

BACKGROUND: Tissue preservation and tumor clearance are hallmarks of Mohs micrographic surgery, but no standardized method currently exists to guide trainees on how to balance the two. OBJECTIVE: The authors provided residents and fellows with additional histologic information to enhance their surgical decision-making without changing the standard methodology of Mohs surgery. METHODS AND MATERIALS: Trainees were provided initial biopsy slides (IS) and frozen vertical sections (VS) of the first Mohs layer. All Mohs layers were excised in standard fashion, and vertically oriented sections were taken from the layer without disturbing the surgical margins to obtain VS. Surveys were used to assess trainees' confidence in performing Mohs surgery with and without these tools. RESULTS: Trainees reported increased confidence in performing Mohs surgery when they reviewed IS before surgery and viewed VS of the first layer. CONCLUSION: Reviewing IS and VS improved trainees' confidence in performing Mohs surgery. This additional histological information was obtained while maintaining the usual steps of Mohs surgery. Objective information obtained from IS and VS may explain why trainees' confidence increased using this technique. Both IS and VS can be valuable teaching tools that may enhance trainees' ability to perform Mohs surgery.

Optimizing Ideal Thickness of Sections for Epidermis in Intra-Operative Frozen Sections.

AIM AND OBJECTIVES: To estimate and evaluate the optimal thickness of tissue section for skin and dermal appendages intra-operatively and to compare the morphology and architecture of the epidermis and its appendages at 7 and 10 microns. METHODOLOGY: After obtaining clearance from the institutional human ethical committee, 101 skin margins were prospectively analyzed using a two-step embedding technique. After multiple trials and errors, 7- and 10-micron thicknesses were selected for the present study. Artefacts, staining characteristics, cellular morphology, cellular outline, and nuclear outline were assessed and scored as unacceptable or acceptable. The data were entered in a Microsoft Excel spreadsheet and analyzed using SPSS software. RESULTS: There was a statistically significant difference between the sections obtained at 7 microns and 10 microns (p-value: <0.001), the latter were better in all the parameters analyzed. However, no difference was noted in the characteristics of the dermal appendages (p-value: >0.05). CONCLUSION: While mucosal margins can be obtained at the usual 5-7 microns, the same thickness is not optimal for skin margins intra-operatively. Frozen sections for the skin margins may be set at 10 microns, to save time, minimize artefacts, and for better readability.

Fluorescence Assisted Stereotactic Biopsy of Contrast-Enhancing Brain Lesions: Can YELLOW 560-nm Filter Substitute Frozen Section?

BACKGROUND: The factors on which the accuracy of stereotactic brain biopsy depends are the competence of the neurosurgeon in obtaining a representative sample and the ability of the neuropathologist to make a histological diagnosis from a minuscule sample. Over the years intraoperative frozen section has enhanced the diagnostic yield of this minimally invasive procedure. Use of fluorescence in achieving a greater extent of resection is well-established in contemporary neurosurgical practice. This ability of brain tumors to take up the fluorescein sodium dye and glow under the YELLOW 560-nm filter has been utilized in a handful of studies to increase the diagnostic accuracy of stereotactic biopsy. METHODS: We performed a prospective study where the fluorescein sodium dye was injected at a low dose and fluorescence of the biopsied core was compared with that of a tissue obtained from the normal parenchyma. Sample was labeled 'truly fluorescent' only when the glow was more than that of the tissue from normal parenchyma. RESULTS: On cross-tabulating the index test (true fluorescence status) and the reference standard test (final histopathological report) the sensitivity of acquiring a representative sample was found to be 94.74%, specificity was 100%. The positive predictive value and negative predictive value were calculated to be 100% and 50% respectively. The diagnostic yield was comparable to that of the intraoperative frozen section. CONCLUSION: The use of the YELLOW 560-nm filter can make stereotactic biopsy faster, safer, less cumbersome, and more cost-effective, and can be used as a substitute for the frozen section in resource-constrained centers.

Diagnostic Yield of Stereotactic Brain Biopsy in a Sub-Saharan Tertiary Center: A Comprehensive 10-Year Retrospective Analysis.

BACKGROUND: Stereotactic brain biopsy is a crucial minimally invasive surgical technique leveraged to obtain tissue specimens from deep-seated intracranial lesions, offering a safer alternative to open craniotomy for patients who cannot tolerate the latter. Despite its effectiveness, the diagnostic yield varies across different centers and has not been widely studied in Sub-Saharan Africa. METHODS: A single-center retrospective analysis was conducted on 67 consecutive stereotactic brain biopsy procedures carried out by experienced neurosurgeons between January 2012 and December 2022 at a tertiary center in Sub-Saharan Africa. Preoperative clinical status, biopsy type, postoperative complication rate, and histological diagnosis were meticulously analyzed. Factors associated with negative biopsy results were identified using IBM Statistical Package for the Social Sciences SPSS version for Mac, with Fisher exact test employed to detect differences in patient characteristics. Statistical significance was pegged at P < 0.05. RESULTS: The overall diagnostic yield rate was 67%. Major contributors to negative biopsy outcomes were superficial location of the lesion, lesion size less than 10 cc, and the use of the Cape Town Stereotactic System. Enhanced yield rates of up to 93% were realized through the application of magnetic resonance imaging-based images, Stealth Station 7, and frozen section analysis. No correlation was observed between the number of cores obtained and the yield rate. Procedure complications were negligible, and no procedure-related mortality was recorded. CONCLUSIONS: The diagnostic yield rate from our study was somewhat lower than previously reported in contemporary literature, primarily attributed to the differing definitions of diagnostic yield, the dominant use of the older framed Cape Town Stereotactic System, computed tomography-based imaging, and the absence of intraoperative frozen section. Nevertheless, biopsies conducted using the frameless system were comparable with studies from other global regions. Our findings reaffirm that stereotactic brain biopsy when complemented with magnetic resonance imaging-based imaging, frameless stereotactic systems and intraoperative frozen section is a safe, effective, and reliable method for obtaining histological diagnosis.

Can We Do Breast-Conserving Surgery Without Intraoperative Frozen Section of Margin?

PURPOSE: This study was a retrospective and nonrandomized study to assess the safety and reliability of identifying the surgical margin in breast cancer breast-conserving surgery (BCS) by using intraoperative ultrasonic location and specimen mammography instead of traditional intraoperative frozen pathological section. METHODS: Among the patients who underwent BCS from May 2019 to October 2021, according to the different methods of evaluating the intraoperative margin, 104 breast cancer patients were included in the frozen edge group, 53 breast cancer patients were included in the freeze-free group, and the surgeon judged whether extended resection was needed based on the results of pathological section or evaluation of intraoperative ultrasound and mammography. The surgical margins of the two groups were judged by postoperative pathological results as the gold standard. RESULTS: The median waiting pathology results time in the frozen edge group was 64 minutes, while the waiting time in the freeze-free group was 30 minutes, and the difference was statistically significant (P < .0001). The postoperative pathological results showed that the positive rate of the surgical margin in the frozen edge group was 0.96%. The coincidence rate of intraoperative frozen and postoperative pathological results was 99.04%. The coincidence rate between intraoperative mammography and postoperative pathological results was 100%. CONCLUSIONS: In BCS, the method of using intraoperative staining markers combined with mammography to evaluate the resection margin is highly accurate, reliable, economical and convenient, and at the same time reduces the waiting time of the operator during the operation. However, this was not a randomized controlled study, and there was patient selection bias, and its safety needs to be confirmed by long-term follow-up. In the future, it is expected to become the mainstream means of evaluating.

Neurosarcoidosis: Frozen section rescue for a big mimicker - A case report.

Neurosarcoidosis is an uncommon but potentially serious manifestation of sarcoidosis. Diagnosis may be particularly challenging especially when neurosarcoidosis occurs in isolation or is the initial presentation of the systemic disease. The authors take this opportunity to report a case of neurosarcoidosis, presenting as the first manifestation of the disease, diagnosed on frozen section, occurring in a 43-year-old male patient with no past history or manifestation of sarcoidosis.

Diagnostic accuracy of intraoperative frozen section for margin evaluation of oral cavity squamous cell carcinoma.

OBJECTIVES: Intraoperative frozen-section evaluation is a valuable technique for detecting positive margins intraoperatively for oral squamous cell carcinoma. We conducted this study to determine the diagnostic accuracy of frozen section in detecting margin status and the effect of tumor grade and stage on diagnostic accuracy. RESULTS: A total of 251 biopsy-proven cases of oral squamous cell carcinoma were included in this study. The tissue specimen resected during surgery was sent to the laboratory for frozen section evaluation. The frozen section results were then compared with the permanent section results to determine the sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy. The mean age of the patients included in the study was 51.65 ± 10.03 years, with male predominance (55.4%). The overall sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of frozen section were 88.81%, 94.84%, 95.20%, 88.10%, and 91.63%, respectively. We conclude that frozen section is a useful technique in determining the margin status intraoperatively in oral cancers, with high diagnostic accuracy. Moreover, certain clinical parameters such as age, gender, disease duration, and tumor stage and grade appear to affect the diagnostic accuracy of frozen section.

Improving frozen section evaluation of procurement donor kidney biopsies and reducing the discard rate: a promising role for artificial intelligence.

There is a worldwide shortage of deceased-donor kidneys available for transplantation, with too many patients dying while on waiting lists for organs. Meanwhile, and particularly in the United States, many recovered kidneys are discarded, often based on results of frozen section evaluation of a screening biopsy read by an on-call pathologist with limited renal pathology experience. A study in this month's issue of Kidney International uses an artificial intelligence-based approach to evaluate these biopsies, which not only improved correlation between biopsy findings and short-to-intermediate term graft survival, but also demonstrated the potential to reduce biopsy-associated organ discard rates by 25% to 30%.

Analysis of false reasons based on the artificial intelligence RRCART model to identify frozen sections of lymph nodes in breast cancer.

BACKGROUND: Breast cancer is the most common malignant tumor in the world. Intraoperative frozen section of sentinel lymph nodes is an important basis for determining whether axillary lymph node dissection is required for breast cancer surgery. We propose an RRCART model based on a deep-learning network to identify metastases in 2362 frozen sections and count the wrongly identified sections and the associated reasons. The purpose is to summarize the factors that affect the accuracy of the artificial intelligence model and propose corresponding solutions. METHODS: We took the pathological diagnosis of senior pathologists as the gold standard and identified errors. The pathologists and artificial intelligence engineers jointly read the images and heatmaps to determine the locations of the identified errors on sections, and the pathologists found the reasons (false reasons) for the errors. Through NVivo 12 Plus, qualitative analysis of word frequency analysis and nodal analysis was performed on the error reasons, and the top-down error reason framework of "artificial intelligence RRCART model to identify frozen sections of breast cancer lymph nodes" was constructed based on the importance of false reasons. RESULTS: There were 101 incorrectly identified sections in 2362 slides, including 42 false negatives and 59 false positives. Through NVivo 12 Plus software, the error causes were node-coded, and finally, 2 parent nodes (high-frequency error, low-frequency error) and 5 child nodes (section quality, normal lymph node structure, secondary reaction of lymph nodes, micrometastasis, and special growth pattern of tumor) were obtained; among them, the error of highest frequency was that caused by normal lymph node structure, with a total of 45 cases (44.55%), followed by micrometastasis, which occurred in 30 cases (29.70%). CONCLUSIONS: The causes of identification errors in examination of sentinel lymph node frozen sections by artificial intelligence are, in descending order of influence, normal lymph node structure, micrometastases, section quality, special tumor growth patterns and secondary lymph node reactions. In this study, by constructing an artificial intelligence model to identify the error causes of frozen sections of lymph nodes in breast cancer and by analyzing the model in detail, we found that poor quality of slices was the preproblem of many identification errors, which can lead to other errors, such as unclear recognition of lymph node structure by computer. Therefore, we believe that the process of artificial intelligence pathological diagnosis should be optimized, and the quality control of the pathological sections included in the artificial intelligence reading should be carried out first to exclude the influence of poor section quality on the computer model. For cases of micrometastasis, we suggest that by differentiating slices into high- and low-confidence groups, low-confidence micrometastatic slices can be separated for manual identification. The normal lymph node structure can be improved by adding samples and training the model in a targeted manner.

Real-Time Telepathology Is Substantially Equivalent to In-Person Intraoperative Frozen Section Diagnosis.

CONTEXT.­: Intraoperative diagnosis by frozen section is a mainstay of surgical pathology practice, providing immediate feedback to the surgical team. Despite good accuracy with modern methods, access to intraoperative surgical pathology with an appropriate turnaround time (TAT) has been a limiting factor for small or remote surgical centers, with negative impacts on cost and patient care. Telepathology offers immediate expert anatomic pathology consultation to sites without an in-house or subspecialized pathologist. OBJECTIVE.­: To assess the utility of live telepathology in frozen section practice. DESIGN.­: Frozen section diagnoses by telemicroscopy from 2 tertiary care centers with a combined 3 satellite hospitals were queried for anatomic site, TAT per block, pathologist, and concordance with paraffin diagnosis. TAT and concordance were compared to glass diagnoses in the same period. RESULTS.­: For 748 intraoperative diagnoses by telemicroscopy, 694 had TATs with a mean of 18 minutes 56 seconds ± 8 minutes 45 seconds, which was slower than on glass (14 minutes 25 seconds ± 7 minutes 8 seconds, P < .001). Twenty-two (2.89% of available) were discordant, which was not significantly different from the on-glass rate (P = .44) or categorical distribution (P = .31). Two cases (0.27%) had technical failures. CONCLUSIONS.­: Although in-person diagnoses were statistically faster, the great majority of telemicroscopic diagnoses were returned in less than 20 minutes. This remained true through numerous pathologists, pathology assistants and/or technicians, different hospitals, and during a combined 6 years. The concentration of discordant diagnoses among relatively few pathologists suggests individual comfort with telepathology and/or frozen section diagnosis. In rare cases, technical issues prevented telemicroscopic diagnosis. Overall, this justifies continued use and expansion of telemicroscopic services in primary intraoperative diagnoses.

Assessment of large droplet fat in frozen sections of donor liver biopsies: utility and interobserver variability of the newly described Banff method compared to a simplified Average of Fields method.

AIMS: There is great variability in the assessment and reporting of fat in frozen sections of donor liver biopsies. The Banff Working Group has proposed a novel method and definition for scoring large droplet fat (LDF) in donor liver biopsies. This study compares the Banff method with a simpler Average of Fields (AF) method and evaluates the impact of different LDF definitions. METHODS: Three pathologists assessed percentage of LDF (LDF%) in 10 donor liver biopsies using Banff and AF methods, applying the Banff LDF definition (cell distention with a single droplet larger than adjacent hepatocytes). Additionally, LDF% by the AF method was compared using two LDF definitions: Banff definition versus LDF definition 2 (single fat droplet occupying greater than half of a hepatocyte with nuclear displacement). RESULTS: Intraobserver concordance between the Banff and AF methods was similar for all three pathologists (kappa 0.76-1). Both methods exhibited 70% interobserver concordance, and there was substantial agreement (kappa 0.68) in the LDF% among the three pathologists for both methods. Comparing the two LDF definitions, results were significantly lower with the Banff definition; LDF >50% was observed in four cases with LDF definition 2 but none of the cases with the Banff definition. CONCLUSIONS: There is high interobserver and intraobserver concordance of LDF% between the Banff and AF methods. LDF% determined by the Banff definition was lower than with LDF definition 2, and needs to be validated based on graft outcome before it can be recommended for clinical use.

A deep learning algorithm to detect cutaneous squamous cell carcinoma on frozen sections in Mohs micrographic surgery: A retrospective assessment.

Intraoperative margin analysis is crucial for the successful removal of cutaneous squamous cell carcinomas (cSCC). Artificial intelligence technologies (AI) have previously demonstrated potential for facilitating rapid and complete tumour removal using intraoperative margin assessment for basal cell carcinoma. However, the varied morphologies of cSCC present challenges for AI margin assessment. The aim of this study was to develop and evaluate the accuracy of an AI algorithm for real-time histologic margin analysis of cSCC. To do this, a retrospective cohort study was conducted using frozen cSCC section slides. These slides were scanned and annotated, delineating benign tissue structures, inflammation and tumour to develop an AI algorithm for real-time margin analysis. A convolutional neural network workflow was used to extract histomorphological features predictive of cSCC. This algorithm demonstrated proof of concept for identifying cSCC with high accuracy, highlighting the potential for integration of AI into the surgical workflow. Incorporation of AI algorithms may improve efficiency and completeness of real-time margin assessment for cSCC removal, particularly in cases of moderately and poorly differentiated tumours/neoplasms. Further algorithmic improvement incorporating surrounding tissue context is necessary to remain sensitive to the unique epidermal landscape of well-differentiated tumours, and to map tumours to their original anatomical position/orientation.

Accuracy of frozen section remote subspecialty consultation using real-time telepathology and whole-slide imaging in gynecologic cases.

OBJECTIVES: Intrapathology consultation is recommended for complex cases during frozen section (FS) as routine practice. In our institution, solicited second opinions were traditionally provided by in-person consultation (IPC). Whole-slide imaging (WSI) was implemented in 2018 as an alternative but replaced by videoconferencing in 2020. Here, we assess the accuracy of remote FS consultation using these digital modalities vs IPC. METHODS: Gynecologic FS cases over a 4-year period overseen by 2 intraoperative consultants were grouped by consultation method: (1) IPC, (2) WSI, and (3) videoconferencing. Accuracy was determined by concordance between the FS and final report diagnoses. Turnaround time between the 3 groups was analyzed using SPSS statistical software (IBM). RESULTS: Using WSI and videoconferencing, 100% concordance was observed, while the IPC group had a 98.5% concordance rate. Videoconferencing, however, showed longer turnaround times (mean, 45.59 minutes) than IPC (mean, 33.36 minutes). Although turnaround time positively correlated with the number of FS specimens, blocks, and H&E slides per case, no statistically significant differences in the number of specimens, blocks, and H&E slides generated were found among the consultation methods. CONCLUSIONS: Even though turnaround time using videoconferencing is longer, the accuracy of WSI and videoconferencing for remote FS consultation is equivalent to IPC. It is therefore a safe method for conducting intrapathology FS consultation in challenging surgical cases.

Frozen Section Timeout: Pilot Study to Reconcile Margins Using 3D Resected Specimen and Defect Scans.

OBJECTIVE: Opportunities exist to improve intraoperative communication and documentation of resection margin details. We instituted a "frozen section timeout" that centers around visualization of the paired resection specimen and surgical defect-facilitating effective, bidirectional exchange of information. METHODS: We designed an interactive form for use during the "frozen section timeout" including annotated 3D virtual models of the resected specimen and surgical defect, plus a "line-item" table for primary and supplemental margin results. The "timeout" was conducted over a Zoom call between the operating room and frozen section laboratory. The form was simultaneously projected and discussed while all members of the surgical care team stopped activities. Nurses, co-surgeons, and all other members of the surgical team were encouraged to take part in this process. RESULTS: Twenty-six frozen section timeouts were conducted during head and neck surgeries in the Department of Otolaryngology at Mount Sinai West Hospital. These timeouts were facilitated by the lead surgeon, and all other activities were halted to ensure that critical information was shared, documented, and agreed upon. During the timeout, the annotated specimen and defect scans were displayed, clearly demonstrating the at-risk margins and the corresponding location and breadth of supplemental margins harvested. CONCLUSION: Incorporating a frozen section timeout can improve intraoperative communication, increase transparency, and potentially eliminate uncertainty regarding margin status and tumor clearance. Visualization of at-risk margins and the corresponding location and breadth of supplemental margins promises an unprecedented level of documentation and understanding. This novel technique can establish a new and improved standard of care. LEVEL OF EVIDENCE: NA Laryngoscope, 134:725-731, 2024.

Intraoperative pathologic diagnosis of central nervous system lymphomas: A comparison of frozen and permanent section diagnoses, and the significance of preoperative imaging.

BACKGROUND: Central nervous system (CNS) lymphomas, either primary or secondary in origin, are rare malignant tumors affecting the brain, spinal cord, or leptomeninges. Diagnosis of CNS lymphomas is complicated by their diverse clinical presentations, radiological features, and histopathological characteristics. Although frozen section (FS) analysis is commonly employed for various CNS tumors, its role and accuracy in CNS lymphoma diagnosis are less explored. In this study, we conducted a comparative analysis to assess the impact of knowledge of preoperative imaging on enhancing the accuracy of FS diagnosis in CNS lymphomas. METHODS: Data collection involved a retrospective review of CNS lymphoma patients from January 2009 to August 2021. Patients who underwent intraoperative consultation were included, excluding those with prior cortisone treatment. The dataset incorporated patient demographics, classification as primary or secondary lymphoma, radiological preliminary diagnoses, FS diagnosis, and permanent section diagnosis. We employed various archived materials, including FSs, touch imprint slides, crush cytology slides, H&E-stained sections, and immunohistochemical stains, and re-evaluated all slides for diagnostic validation. RESULTS: Our study included 25 patients, of whom 60 % were female and had a mean age of 56.5 years. Preoperative radiology data were available for 80 % of cases, with preliminary diagnoses commonly including lymphoma and/or metastasis. Intraoperative consultation results indicated lymphoma in 18 (72 %) patients, with discordance observed in 28 % of cases when compared to permanent section diagnoses. Most permanent section diagnoses were diffuse large B-cell lymphomas (92 %), with the remainder being T-cell non-Hodgkin lymphoma (4 %) and follicular lymphoma (4 %). Intraoperative misdiagnoses were significantly associated with the absence of knowledge of preoperative imaging. CONCLUSION: Our study demonstrates the reliability of FS diagnosis for CNS lymphomas during surgery, with a favorable complete concordance rate of 72 % when compared to permanent diagnoses. Importantly, lack of knowledge of preoperative imaging significantly impaired diagnostic accuracy in FS, emphasizing the need for close collaboration between pathologists and radiologists.

A biosensor for D-2-hydroxyglutarate in frozen sections and intraoperative assessment of IDH mutation status.

The oncometabolite D-2-hydroxyglutarate (D-2-HG) has emerged as a valuable biomarker in tumors with isocitrate dehydrogenase (IDH) mutations. Efficient detection methods are required and rapid intraoperative determination of D-2-HG remains a huge challenge. Herein, D-2-HG dehydrogenase from Achromobacter xylosoxidans (AX-D2HGDH) was found to have high substrate specificity. AX-D2HGDH dehydrogenizes D-2-HG and reduces flavin adenine dinucleotide (FAD) bound to the enzyme. Interestingly, the dye resazurin can be taken as another substrate to restore FAD. AX-D2HGDH thus catalyzes a bisubstrate and biproduct reaction: the dehydrogenation of D-2-HG to 2-ketoglutarate and simultaneous reduction of non-fluorescent resazurin to highly fluorescent resorufin. According to steady-state analysis, a ping-pong bi-bi mechanism has been concluded. The Km values for resazurin and D-2-HG were determined as 0.56 µM and 10.93 µM, respectively, suggesting high affinity to both substrates. On the basis, taking AX-D2HGDH and resazurin as recognition and fluorescence transducing element, a D-2-HG biosensor (HGAXR) has been constructed. HGAXR exhibits high sensitivity, accuracy and specificity for D-2-HG in different biological samples. With the aid of HGAXR and the matched low-cost palm-size detecting device, D-2-HG levels in frozen sections of resected brain tumor tissues can be measured in a direct, simple and accurate manner with a fast detection (1-3 min). As the technique of frozen section is familiar to surgeons and pathologists, HGAXR and the portable device can be easily integrated into the current workflow, having potential to provide rapid intraoperative pathology for IDH mutation status and guide decision-making during surgery.