Unique Approach for Isolating Rat Bone Marrow Neutrophils with Comparable Capacity.

The primary aim of this research was to develop a reliable and efficient approach for isolating neutrophil extracellular traps (NETs) from rat bone marrow. This effort arose due to limitations associated with the traditional method of extracting NETs from peripheral blood, mainly due to the scarcity of available neutrophils for isolation. The study revealed two distinct methodologies for obtaining rat neutrophils from bone marrow: a streamlined one-step procedure that yielded satisfactory purification levels, and a more time-intensive two-step process that exhibited enhanced purification efficiency. Importantly, both techniques yielded a substantial quantity of viable neutrophils, ranging between 50 to 100 million per rat. This efficiency mirrored the results obtained from isolating neutrophils from both human and murine sources. Significantly, neutrophils derived from rat bone marrow exhibited comparable abilities to secrete NETs when compared with neutrophils obtained from peripheral blood. However, the bone marrow-based method consistently produced notably larger quantities of both neutrophils and NETs. This approach demonstrated the potential to obtain significantly greater amounts of these cellular components for further downstream applications. Notably, these isolated NETs and neutrophils hold promise for a range of applications, spanning the realms of inflammation, infection, and autoimmune diseases.

Impression cytology of ocular surface in xeroderma pigmentosum.

PURPOSE: To describe cellular alterations detected by impression cytology of the ocular surface in patients with xeroderma pigmentosum. The secondary objective was to assess the reliability of impression cytology in diagnosing ocular surface squamous neoplasia. METHODS: Patients with xeroderma pigmentosum underwent a single-day complete ophthalmological examination and impression cytology for ocular surface evaluation using 13 mm diameter mixed cellulose esters membrane filters and combined staining with Periodic Acid Schiff, Hematoxylin and Eosin, and Papanicolaou stains followed by microscopic analysis. The cytological findings were correlated with the clinical diagnosis. The impression cytology findings at baseline and one-year follow-up were correlated with the clinical course (no tumor, treated tumor, residual tumor recurrent tumor, new tumor). RESULTS: Of the 42 patients examined, impression cytology was performed in 62 eyes of 34 participants (65% females). The mean age of patients was 29.6 ± 17 years (range 7-62). Fifteen eyes had a clinical diagnosis of ocular surface squamous neoplasia. Impression cytology showed goblet cells (47, 75%), inflammatory cells (12, 19%), keratinization (5, 8%), and squamous metaplasia (30, 48%). Impression cytology was positive for atypical cells in 18 patients (12 with and 6 without ocular surface squamous neoplasia). The sensitivity, specificity, positive predictive value, and negative predictive value of impression cytology (at baseline) for diagnosis of ocular surface squamous neoplasia were 80%, 87%, 67%, and 93%, respectively, using clinical diagnosis of ocular surface squamous neoplasia as the reference standard. CONCLUSION: Impression cytology has a moderate positive predictive value for the diagnosis of ocular surface squamous neoplasia in patients with xeroderma pigmentosum. However, the lack of detection of atypical cells on impression cytology has a high negative predictive value for ocular surface squamous neoplasia. Integration of impression cytology in the long-term management of high-risk patients, such as patients with xeroderma pigmentosum, can avoid unnecessary diagnostic biopsies.

Cell block practices in European cytopathology laboratories.

BACKGROUND: There are numerous methods and procedures described for the preparation of cell blocks (CBs) from cytological samples. The objective of this study was to determine current practices and issues with CBs in European laboratories. METHODS: A link to an online survey, with 11 questions about CB practices, was distributed to cytology laboratories via participants of United Kingdom National External Quality Assurance Service for Cellular Pathology Techniques and national representatives in the European Federation of Cytology Societies. RESULTS: A total of 402 laboratories responded completely (337/402, 84%) or partially (65/402, 16%) to the survey by February 4, 2022. The most common CB practice is embedding cell pellets using plasma and thrombin (23.3%), agar (17.1%), Shandon/Epredia Cytoblock (11.4%), HistoGel (7.9%), and Cellient (3.5%). Other methods such as CytoFoam, albumin, gelatin, Cytomatrix, and collodion bags are rarely used (1.0%, 0.7%, 0.7%, 0.3%, and 0.2%, respectively). CBs are also prepared from naturally occurring clots or tissue fragments (29.5%) and cells scraped from unstained or prestained smears (4.4%). The most frequent issues with the CBs in a daily cytology practice are low cellularity (248/402, 62%) and dispersed cells (89/402, 22%), regardless of the CBs preparation method or how the samples for embedding were selected. CONCLUSIONS: There is a great variability in CB practices in European laboratories with low cellular CBs as the main issue. Additional studies are mandatory to evaluate and improve performance and cellular yield of CBs.

Telecytology - remote rapid on-site evaluation for ultrasound-guided head and neck fine needle aspiration utilising a clinical imaging assistant with an extended practice role.

OBJECTIVE: Rapid On-Site Evaluation (ROSE) of fine needle aspirations (FNA) is widely accepted as best practice, resulting in better outcomes and delivery of care for patients. However, it is not always practical for cytology laboratories to release staff. To increase the availability of ROSE, this study aimed to robustly test the effectiveness of Telecytology ROSE (TCROSE) utilising a clinical imaging assistant (CIA) to prepare the samples and operate the microscope. METHODS: The study was divided into 3 phases. Phase 1, equipment testing, validation and in-house training for the CIA and the Consultant Biomedical Scientist (CBMS) performing TCROSE. Phase 2, Verifying TCROSE on the same site as the cytology laboratory and phase 3, TCROSE utilising a clinic at a peripheral site away from the cytology laboratory. RESULTS: 78/80 (97% sensitivity, 95% accuracy) of TCROSE cases matched the final report for assessment of adequacy and sufficient sampling, demonstrating 94% reliability with a 95% confidence value. An appropriately trained CIA effectively prepared the samples and operated the microscope for remote interpretation. The samples were triaged effectively, and biopsy requests were appropriate to reduce the need for repeat procedures and delays in treatment. This approach received positive feedback from patients. CONCLUSION: TCROSE utilising a CIA provides a highly effective alternative to conventional ROSE, minimising the resources required from cytopathology services and improving patient care and access to best practice. This study supports the validity of trained CIAs for a more involved role in the ultrasound-guided FNA service.

A review of the directly sampled endometrial cytology on LBC samples: Classification, microscopic criteria and beyond.

The Yokohama System for Reporting Endometrial Cytology (TYS) has been proposed by an expert meeting under the auspices of the International Academy of Cytology (IAC) in May 2016 at the IAC in Yokohama. Since its introduction, the TYS has been receiving worldwide acceptance, and this review aims to assess its global impact. The adoption of endometrial cytology as a diagnostic procedure has been hampered in the past by difficulties arising in interpreting the cellular findings due to a number of factors (such as excess blood, cellular overlapping and the complex physiology of endometrium). Recently, the use of liquid-based cytology (LBC), with its ability to remove blood and mucus and to distribute cells uniformly in a thin layer on the slide, has provided an opportunity to re-evaluate the role of endometrial cytology. LBC is a useful tool in the cytologic diagnosis and follow-up of endometrial abnormalities, which remains complementary to the emerging molecular diagnostic cytopathology. The study of LBC from endometrial cytology could be challenging since it is affected by numerous look-alikes and diagnostic pitfalls. This review discusses these various entities and takes into consideration the ancillary techniques that may be useful in the diagnostic procedure. In conclusion, our review of the published data suggests that the TYS is a valid classification scheme that has been widely accepted by cytopathologists globally, is highly reproducible and makes a valuable contribution to clinical therapeutic management. At present, molecular cytopathology is a rapidly evolving field of modern cytopathology, which underlines the effective interplay between genomics and cytology. This review aims to provide a comprehensive review of the drawbacks of endometrial cytopathology, particularly in terms of endometrial cancer diagnosis and molecular testing.

Density-Based Fractionation of Cell-Conditioned Medium to Prepare Proteomics Grade Extracellular Vesicles.

The identification of the molecular composition of extracellular vesicles (EV) by omics approaches, including proteomics, requires the separation of EV from non-EV confounding factors present in the source biofluid. In this protocol, we present the sequential implementation of density gradient ultracentrifugation and size-exclusion chromatography to prepare EV from cell-conditioned medium with high specificity and repeatability. This approach enables the recovery of intact purified EV suited for downstream functional assays and biomarker discovery by omics approaches.

Remotely operated robotic microscopy for rapid diagnosis of bronchoscopic cytology specimens.

BACKGROUND: Obtaining a diagnosis and treating pulmonary malignancies during the same anesthesia requires either an on-site pathologist or a system for remotely evaluating microscopic images. Cytology specimens are challenging to remotely assess given the need to navigate through dispersed and three-dimensional cell clusters. Remote navigation is possible using robotic telepathology, but data are limited on the ease of use of current systems, particularly for pulmonary cytology. METHODS: Air dried modified Wright-Giemsa stained slides from 26 touch preparations of transbronchial biopsies and 27 smears of endobronchial ultrasound guided fine needle aspirations were scored for ease of adequacy assessment and ease of diagnosis on robotic (rmtConnect Microscope) and non-robotic telecytology platforms. Diagnostic classifications were compared between glass slides and the robotic and non-robotic telecytology assessments. RESULTS: Compared to non-robotic telecytology, robotic telecytology had a greater ease of adequacy assessment and non-inferior ease of diagnosis. The median time to diagnosis using robotic telecytology was 85 s (range 28-190 s). Diagnostic categories were concordant for 76% of cases in robotic versus non-robotic telecytology and 78% of cases in robotic telecytology versus glass slide diagnosis. Weighted Cohen's kappa scores for agreement in these comparisons were 0.84 and 0.72, respectively. CONCLUSIONS: Use of a remote-controlled robotic microscope improved the ease of adequacy assessment compared to non-robotic telecytology and enabled strongly concordant diagnoses to be expediently rendered. This study provides evidence that modern robotic telecytology is a feasible and user-friendly method of remotely and potentially intraoperatively rendering adequacy assessments and diagnoses on bronchoscopic cytology specimens.

An engineered cell line with a hRpn1-attached handle to isolate proteasomes.

Regulated protein degradation in eukaryotes is performed by the 26S proteasome, which contains a 19-subunit regulatory particle (RP) that binds, processes, and translocates substrates to a 28-subunit hollow core particle (CP) where proteolysis occurs. In addition to its intrinsic subunits, myriad proteins interact with the proteasome transiently, including factors that assist and/or regulate its degradative activities. Efforts to identify proteasome-interacting components and/or to solve its structure have relied on over-expression of a tagged plasmid, establishing stable cell lines, or laborious purification protocols to isolate native proteasomes from cells. Here, we describe an engineered human cell line, derived from colon cancer HCT116 cells, with a biotin handle on the RP subunit hRpn1/PSMD2 (proteasome 26S subunit, non-ATPase 2) for purification of 26S proteasomes. A 75-residue sequence from Propionibacterium shermanii that is biotinylated in mammalian cells was added following a tobacco etch virus protease cut site at the C terminus of hRpn1. We tested and found that 26S proteasomes can be isolated from this modified HCT116 cell line by using a simple purification protocol. More specifically, biotinylated proteasomes were purified from the cell lysates by using neutravidin agarose resin and released from the resin following incubation with tobacco etch virus protease. The purified proteasomes had equivalent activity in degrading a model ubiquitinated substrate, namely ubiquitinated p53, compared to commercially available bovine proteasomes that were purified by fractionation. In conclusion, advantages of this approach to obtain 26S proteasomes over others is the simple purification protocol and that all cellular proteins, including the tagged hRpn1 subunit, remain at endogenous stoichiometry.

Application of CytoMatrix for the diagnosis of melanoma metastases on FNA cytology samples: Performance of a novel cell block method.

BACKGROUND: The management of cytological samples can significantly impact diagnostic interpretation. Cell blocks (CB) are a popular method due to their ability to provide additional morphological information and be used for immunocytochemistry and molecular tests. Recently, a new CB technique called the synthetic matrix CytoMatrix (CM) has been introduced, which can gather and hold cytological material within its three-dimensional structure. METHODS: In this study, 40 cytological samples from patients with melanoma metastases were analyzed to evaluate the diagnostic performance of CM compared to another CB method used in the laboratory. The researchers assessed the morphological adequacy of the two techniques, as well as their performance in immunocytochemical analysis and molecular. RESULTS: This study showed that CM was quicker and equally effective compared to the other method, with the laboratory technician having less of an impact on the CM approach across all passages. Additionally, all CMs were adequate, whereas the other method was adequate in 90% of cases. Immunocytochemistry confirmed the diagnosis of melanoma metastases in all cases, and all 40 CMs and 36 of the other method were adequate for fluorescence in situ hybridization analysis. CONCLUSION: CM is a low-time-consuming technology that is unaffected by technicians during all setup phases, making it simpler to standardize the procedure. Moreover, a low loss of diagnostic cells ensures greater benefits for morphological analysis, immunocytochemistry, and molecular testing. Overall, the study highlights the potential of CM as a valuable technique for managing cytological samples.

Relationship between a deep learning model and liquid-based cytological processing techniques.

OBJECTIVE: Artificial intelligence (AI)-based cytopathology studies conducted using deep learning have enabled cell detection and classification. Liquid-based cytology (LBC) has facilitated the standardisation of specimen preparation; however, cytomorphology varies according to the LBC processing technique used. In this study, we elucidated the relationship between two LBC techniques and cell detection and classification using a deep learning model. METHODS: Cytological specimens were prepared using the ThinPrep and SurePath methods. The accuracy of cell detection and cell classification was examined using the one- and five-cell models, which were trained with one and five cell types, respectively. RESULTS: When the same LBC processing techniques were used for the training and detection preparations, the cell detection and classification rates were high. The model trained on ThinPrep preparations was more accurate than that trained on SurePath. When the preparation types used for training and detection were different, the accuracy of cell detection and classification was significantly reduced (P < 0.01). The model trained on both ThinPrep and SurePath preparations exhibited slightly reduced cell detection and classification rates but was highly accurate. CONCLUSIONS: For the two LBC processing techniques, cytomorphology varied according to cell type; this difference affects the accuracy of cell detection and classification by deep learning. Therefore, for highly accurate cell detection and classification using AI, the same processing technique must be used for both training and detection. Our assessment also suggests that a deep learning model should be constructed using specimens prepared via a variety of processing techniques to construct a globally applicable AI model.

Laminin switches terminal differentiation fate of human trophoblast stem cells under chemically defined culture conditions.

Human trophoblast stem cells (hTSCs) have emerged as a powerful tool to model early placental development in vitro. Analogous to the epithelial cytotrophoblast in the placenta, hTSCs can differentiate into cells of the extravillous trophoblast (EVT) lineage or the multinucleate syncytiotrophoblast (STB). Here we present a chemically defined culture system for STB and EVT differentiation of hTSCs. Notably, in contrast to current approaches, we neither utilize forskolin for STB formation nor transforming growth factor-beta (TGFß) inhibitors or a passage step for EVT differentiation. Strikingly, the presence of a single additional extracellular cue-laminin-111-switched the terminal differentiation of hTSCs from STB to the EVT lineage under these conditions. In the absence of laminin-111, STB formation occurred, with cell fusion comparable to that obtained with differentiation mediated by forskolin; however, in the presence of laminin-111, hTSCs differentiated to the EVT lineage. Protein expression of nuclear hypoxia-inducible factors (HIF1α and HIF2α) was upregulated during EVT differentiation mediated by laminin-111 exposure. A heterogeneous mixture of Notch1+ EVTs in colonies and HLA-G+ single-cell EVTs were obtained without a passage step, reminiscent of heterogeneity in vivo. Further analysis showed that inhibition of TGFß signaling affected both STB and EVT differentiation mediated by laminin-111 exposure. TGFß inhibition during EVT differentiation resulted in decreased HLA-G expression and increased Notch1 expression. On the other hand, TGFß inhibition prevented STB formation. The chemically defined culture system for hTSC differentiation established herein facilitates quantitative analysis of heterogeneity that arises during hTSC differentiation and will enable mechanistic studies in vitro.

Cell blocks in cytology: review of preparation methods, advantages, and limitations.

Cell blocks are cytologic preparations that are processed as paraffin embedded blocks in a manner comparable to formalin-fixed paraffin-embedded tissue in surgical pathology. In addition to serving as an adjunct to other cytologic preparations for morphologic diagnosis, cell blocks play an increasingly important role as they yield tissue sections that can be utilized for ancillary testing such as immunohistochemical stains and molecular studies. While essentially universally viewed as playing a pivotal role in cytopathology practice, there are various factors that limit their use in practice and contribute to dissatisfaction with cell block quality. Cell block preparation, as opposed to tissue processing in surgical pathology, is more variable with many different protocols in use today. This review explores the most commonly used cell block preparation techniques currently in use with review of the unique advantages and limitations each method presents. The goal of this work is to serve as a resource that can aid in making more informed decisions about which cell block protocol may work best for individual laboratories.

A photo-switchable assay system for dendrite degeneration and repair in Drosophila melanogaster.

Neurodegeneration arising from aging, injury, or diseases has devastating health consequences. Whereas neuronal survival and axon degeneration have been studied extensively, much less is known about how neurodegeneration affects dendrites, in part due to the limited assay systems available. To develop an assay for dendrite degeneration and repair, we used photo-switchable caspase-3 (caspase-Light-Oxygen-Voltage-sensing [caspase-LOV]) in peripheral class 4 dendrite arborization (c4da) neurons to induce graded neurodegeneration by adjusting illumination duration during development and adulthood in Drosophila melanogaster. We found that both developing and mature c4da neurons were able to survive while sustaining mild neurodegeneration induced by moderate caspase-LOV activation. Further, we observed active dendrite addition and dendrite regeneration in developing and mature c4da neurons, respectively. Using this assay, we found that the mouse Wallerian degeneration slow (WldS) protein can protect c4da neurons from caspase-LOV-induced dendrite degeneration and cell death. Furthermore, our data show that WldS can reduce dendrite elimination without affecting dendrite addition. In summary, we successfully established a photo-switchable assay system in both developing and mature neurons and used WldS as a test case to study the mechanisms underlying dendrite regeneration and repair.

Oral brush biopsy using liquid-based cytology is a reliable tool for oral cancer screening: A cost-utility analysis: Oral brush biopsy for oral cancer screening.

BACKGROUND: This study aimed to assess the diagnostic utility and associated cost of oral liquid-based brush cytology (OLBC) in the diagnosis of oral cancer and oral potentially malignant disorders (OPMDs). METHODS: A total of 284 patients with oral mucosal lesions were included. OLBC samples were collected from all patients immediately before undergoing surgical biopsies. A liquid-based cytology slide was prepared from each OLBC sample for cytological evaluation using the modified 2014 Bethesda cytology system. The results and the cost were compared with the histopathological outcomes. RESULTS: The level of agreement between the two approaches was very good (weighted kappa = 0.824). The accuracy of OLBC in differentiating between the different diagnostic groups was 91.69%, whereas the associated sensitivity and specificity were 79.23% and 94.81%, respectively. The estimated cost of each OLBC sample was at least 26% less than the cost of a single biopsy and more than 42% less in cases of multiple biopsied lesions. CONCLUSIONS: The proposed modifications of the Bethesda system can be adopted as a standardized system for oral cytological assessment. Our findings support OLBC as a reliable adjunct to surgical biopsy in the diagnosis of OPMDs. This tool has potential for oral cancer-finding and surveillance programs.

Reassessing the optimal volume for malignancy detection in serous fluid cytology.

BACKGROUND: The international system for reporting serous fluid cytopathology (TIS) recommends submitting at least 50-75 mL of serous fluid to decrease false-negative results. However, prior studies did not agree on specific volume requirements or consensus adequacy criteria. Our study aims to assess whether fluid volume affects the adequacy rate and to assess the minimum volume necessary for optimal adequacy in pleural and peritoneal fluids. METHODS: A total of 8530 serous fluid cytology cases were identified in the laboratory information system. Differences in mean fluid volume received in the laboratory were compared using an ANOVA Games-Howell test based on TIS category. The percentage of malignant diagnoses across the volume ranges of 0 to 5 mL, 5 to 10 mL, 10 to 25 mL, 25 to 50 mL, 50 to 75 mL, 75 to 100 mL, 100 to 150 mL, 150 to 250 mL, 250 to 500 mL, 500 to 2000 mL was compared in pleural and peritoneal fluids using a chi-square test, and a SiZer analysis was performed. RESULTS: Mean fluid volume in inadequate, atypical, and negative cases was significantly lower compared to positive cases. A SiZer analysis showed a positive relationship between the malignancy fraction of pleural and peritoneal fluids and fluid volume. The percentage of malignant diagnoses in pleural and peritoneal fluid samples increased significantly up to a volume range of 75-100 mL. CONCLUSIONS: There is a significant relationship between fluid volume, adequacy and detection of malignancy in serous effusion cytopathology. The malignancy fraction increases with larger fluid volumes but at least 75-100 mL of fluid should be submitted for optimal diagnosis of malignancy in pleural and peritoneal fluids.

Automated human cell classification in sparse datasets using few-shot learning.

Classifying and analyzing human cells is a lengthy procedure, often involving a trained professional. In an attempt to expedite this process, an active area of research involves automating cell classification through use of deep learning-based techniques. In practice, a large amount of data is required to accurately train these deep learning models. However, due to the sparse human cell datasets currently available, the performance of these models is typically low. This study investigates the feasibility of using few-shot learning-based techniques to mitigate the data requirements for accurate training. The study is comprised of three parts: First, current state-of-the-art few-shot learning techniques are evaluated on human cell classification. The selected techniques are trained on a non-medical dataset and then tested on two out-of-domain, human cell datasets. The results indicate that, overall, the test accuracy of state-of-the-art techniques decreased by at least 30% when transitioning from a non-medical dataset to a medical dataset. Reptile and EPNet were the top performing techniques tested on the BCCD dataset and HEp-2 dataset respectively. Second, this study evaluates the potential benefits, if any, to varying the backbone architecture and training schemes in current state-of-the-art few-shot learning techniques when used in human cell classification. To this end, the best technique identified in the first part of this study, EPNet, is used for experimentation. In particular, the study used 6 different network backbones, 5 data augmentation methodologies, and 2 model training schemes. Even with these additions, the overall test accuracy of EPNet decreased from 88.66% on non-medical datasets to 44.13% at best on the medical datasets. Third, this study presents future directions for using few-shot learning in human cell classification. In general, few-shot learning in its current state performs poorly on human cell classification. The study proves that attempts to modify existing network architectures are not effective and concludes that future research effort should be focused on improving robustness towards out-of-domain testing using optimization-based or self-supervised few-shot learning techniques.

Generative adversarial network enables rapid and robust fluorescence lifetime image analysis in live cells.

Fluorescence lifetime imaging microscopy (FLIM) is a powerful tool to quantify molecular compositions and study molecular states in complex cellular environment as the lifetime readings are not biased by fluorophore concentration or excitation power. However, the current methods to generate FLIM images are either computationally intensive or unreliable when the number of photons acquired at each pixel is low. Here we introduce a new deep learning-based method termed flimGANE (fluorescence lifetime imaging based on Generative Adversarial Network Estimation) that can rapidly generate accurate and high-quality FLIM images even in the photon-starved conditions. We demonstrated our model is up to 2,800 times faster than the gold standard time-domain maximum likelihood estimation (TD_MLE) and that flimGANE provides a more accurate analysis of low-photon-count histograms in barcode identification, cellular structure visualization, Förster resonance energy transfer characterization, and metabolic state analysis in live cells. With its advantages in speed and reliability, flimGANE is particularly useful in fundamental biological research and clinical applications, where high-speed analysis is critical.

Diagnostic impact of safety protocols for processing peritoneal washing specimens during the global pandemic of coronavirus disease 2019: A comparative study from 195 cytological samples.

BACKGROUND: The global pandemic of the coronavirus disease 2019 represents a major concern for health services worldwide, and has also induced major changes in cytopathology practice. AIM: We aimed to verify the diagnostic performance of cytological evaluation under a new safety protocol during the pandemic compared to the standard pre-pandemic procedure. We also aimed to assess how cytological diagnoses and sampling were impacted during the pandemic period compared to the pandemic-free period in 2019. MATERIALS AND METHODS: Cytological samples of peritoneal washings taken during the first 10 months of the pandemic emergency in Italy (March 11, 2020 to January 11, 2021) were compared to samples from the preceding 10-month time frame (May 11, 2019 to March 10, 2020). RESULTS: One hundred ninety-five specimens were analysed in the present study. We observed no noticeable differences in cytological diagnoses during the pandemic period compared to the pre-pandemic period. The case numbers by diagnostic category for the pre-pandemic vs pandemic periods, respectively, were as follows: non-diagnostic, 0 vs 0 cases; negative for malignancy, 86 vs 52 cases; atypia of uncertain significance, 7 vs 1 cases; suspicious for malignancy, 0 vs 2 cases; malignant, 42 vs 4 cases. CONCLUSION: While a consistent reduction in the number of cytological examinations has been observed during the COVID-19 period, our institutional safety protocol for processing cytological samples did not affect the diagnostic reliability of peritoneal washing cytology.