The current state of digital cytology and artificial intelligence (AI): global survey results from the American Society of Cytopathology Digital Cytology Task Force.

INTRODUCTION: The integration of whole slide imaging (WSI) and artificial intelligence (AI) with digital cytology has been growing gradually. Therefore, there is a need to evaluate the current state of digital cytology. This study aimed to determine the current landscape of digital cytology via a survey conducted as part of the American Society of Cytopathology (ASC) Digital Cytology White Paper Task Force. MATERIALS AND METHODS: A survey with 43 questions pertaining to the current practices and experiences of WSI and AI in both surgical pathology and cytology was created. The survey was sent to members of the ASC, the International Academy of Cytology (IAC), and the Papanicolaou Society of Cytopathology (PSC). Responses were recorded and analyzed. RESULTS: In total, 327 individuals participated in the survey, spanning a diverse array of practice settings, roles, and experiences around the globe. The majority of responses indicated there was routine scanning of surgical pathology slides (n = 134; 61%) with fewer respondents scanning cytology slides (n = 150; 46%). The primary challenge for surgical WSI is the need for faster scanning and cost minimization, whereas image quality is the top issue for cytology WSI. AI tools are not widely utilized, with only 16% of participants using AI for surgical pathology samples and 13% for cytology practice. CONCLUSIONS: Utilization of digital pathology is limited in cytology laboratories as compared to surgical pathology. However, as more laboratories are willing to implement digital cytology in the near future, the establishment of practical clinical guidelines is needed.

Thyroid nodules with DICER1 mutation or PTEN alteration: A comparative cytologic, clinical, and molecular study of 117 FNA cases.

BACKGROUND: DICER1 mutations and PTEN alterations are increasingly detected by thyroid fine-needle aspiration (FNA). Both are associated with nodular thyroid disease and cancer. The authors analyzed a large comparative thyroid FNA cohort with DICER1 mutation or PTEN alteration. METHODS: A total of 117 thyroid FNAs with DICER1 or PTEN alterations were retrieved from the databases of two academic medical institutions. Demographic, clinical, and radiologic data were collected; FNA slides were analyzed for 29 cytomorphologic features. RESULTS: Of 117 thyroid FNAs, 36 (30.8%) had DICER1 mutation and 81 (69.2%) showed PTEN alteration. The DICER1 cohort had 33 (91.7%) females and three (8.3%) males (mean, 40.9 years); 61.8% had multinodular disease. FNAs were classified as atypia of undetermined significance (AUS), 23 (63.9%); follicular neoplasm (FN), 12 (33.3%); and malignant, 1 (2.8%). The PTEN subgroup had 66 (81.5%) females and 15 (18.5%) males (mean, 55.2 years) with increased multinodular disease (93.8%, p = .0016). PTEN FNAs had greater cytologic diversity: non-diagnostic, 2 (2.5%); benign, 5 (6.2%); AUS, 44 (54.3%); FN, 24 (29.6%); and malignant, 6 (7.4%). Both DICER1 and PTEN cases showed a range of resected tumor subtypes. The DICER1 cohort included thyroblastoma, and the PTEN group included anaplastic carcinoma. The cytomorphology of DICER1 and PTEN cases showed overlapping features, especially microfollicular patterns. Minor cytomorphologic differences included papillary patterns in DICER1 (p = .039), and oncocytic changes (p < .0001) in PTEN. CONCLUSIONS: DICER1 and PTEN FNAs reveal many cytologic similarities. DICER1 patients are younger, and PTEN patients had multinodular disease. Awareness of these genetic cohorts can identify patients at risk for thyroid cancer.

1-L polyethylene glycol + ascorbic acid versus sodium picosulfate + magnesium citrate bowel preparations for colonoscopy: effectiveness and safety.

BACKGROUND: adequate bowel preparation is crucial for the protective effect of colonoscopy. Commonly used preparation regimens like polyethylene glycol (PEG) or sodium picosulfate with magnesium citrate (SPMC) have shown similar results in clinical trials, but low-volume PEG + ascorbic acid (1-L PEG + ASC) versus SPMC have never been compared in a real-life setting. AIM: to evaluate the effectiveness and safety of 1-L PEG + ASC versus SPMC in a real-life setting for the overall population, for patients aged ≥ 65 years, and males versus females. METHODS: out-patients aged ≥ 18 years who underwent colonoscopy for any indication were randomly assigned to the 1-L PEG + ASC or SPMC group. Using the Boston Bowel Preparation Scale (BBPS), the primary endpoints were the bowel cleansing success of the overall colon and right colon, as well as high-quality (HQ) cleansing. Furthermore, the effectiveness and safety outcomes for age groups and males versus females were compared. RESULTS: 1-L PEG + ASC showed significantly better bowel cleansing success than SPMC. Particularly remarkable is the HQ cleansing reached with 1-L PEG + ASC compared with SPMC (55.5 % versus 25.4 % in the overall colon, and 58.7 % versus 27.2 % in the right colon). 1-L PEG + ASC was equally effective for men and women while SPMC showed significant differences between genders (men had worse bowel cleansing). Age did not affect the cleansing effectiveness. 1-L PEG + ASC versus SPMC showed significant differences in tolerance and safety; women also had significantly worse tolerance than men for both solutions, but these did not affect the quality of bowel cleansing. CONCLUSIONS: in our real-life setting, 1-L PEG + ASC offered better adequate and HQ bowel cleansing than SPMC, achieving excellent cleansing quality, regardless of gender or tolerance.

1-L polyethylene glycol + ascorbic acid versus sodium picosulfate + magnesium citrate bowel preparations for colonoscopy: effectiveness and safety

Background: adequate bowel preparation is crucial for the protective effect of colonoscopy. Commonly used preparation regimens like polyethylene glycol (PEG) or sodium picosulfate with magnesium citrate (SPMC) have shown similar results in clinical trials, but low-volume PEG + ascorbic acid (1-L PEG + ASC) versus SPMC have never been compared in a real-life setting. Aim: to evaluate the effectiveness and safety of 1-L PEG + ASC versus SPMC in a real-life setting for the overall population, for patients aged ≥ 65 years, and males versus females. Methods: out-patients aged ≥ 18 years who underwent colonoscopy for any indication were randomly assigned to the 1-L PEG + ASC or SPMC group. Using the Boston Bowel Preparation Scale (BBPS), the primary endpoints were the bowel cleansing success of the overall colon and right colon, as well as high-quality (HQ) cleansing. Furthermore, the effectiveness and safety outcomes for age groups and males versus females were compared. Results: 1-L PEG + ASC showed significantly better bowel cleansing success than SPMC. Particularly remarkable is the HQ cleansing reached with 1-L PEG + ASC compared with SPMC (55.5 % versus 25.4 % in the overall colon, and 58.7 % versus 27.2 % in the right colon). 1-L PEG + ASC was equally effective for men and women while SPMC showed significant differences between genders (men had worse bowel cleansing). Age did not affect the cleansing effectiveness. 1-L PEG + ASC versus SPMC showed significant differences in tolerance and safety; women also had significantly worse tolerance than men for both solutions, but these did not affect the quality of bowel cleansing. Conclusions: in our real-life setting, 1-L PEG + ASC offered better adequate and HQ bowel cleansing than SPMC, achieving excellent cleansing quality, regardless of gender or tolerance. (AU)

Digital cytology part 1: digital cytology implementation for practice: a concept paper with review and recommendations from the American Society of Cytopathology Digital Cytology Task Force.

Digital cytology and artificial intelligence (AI) are gaining greater adoption in the cytopathology laboratory. However, peer-reviewed real-world data and literature are lacking regarding the current clinical landscape. The American Society of Cytopathology in conjunction with the International Academy of Cytology and the Digital Pathology Association established a special task force comprising 20 members with expertise and/or interest in digital cytology. The aim of the group was to investigate the feasibility of incorporating digital cytology, specifically cytology whole slide scanning and AI applications, into the workflow of the laboratory. In turn, the impact on cytopathologists, cytologists (cytotechnologists), and cytology departments were also assessed. The task force reviewed existing literature on digital cytology, conducted a worldwide survey, and held a virtual roundtable discussion on digital cytology and AI with multiple industry corporate representatives. This white paper, presented in 2 parts, summarizes the current state of digital cytology and AI practice in global cytology practice. Part 1 of the white paper presented herein is a review and offers best practice recommendations for incorporating digital cytology into practice. Part 2 of the white paper provides a comprehensive review of AI in cytology practice along with best practice recommendations and legal considerations. Additionally, the results of a global survey regarding digital cytology are highlighted.

Digital cytology part 2: artificial intelligence in cytology: a concept paper with review and recommendations from the American Society of Cytopathology Digital Cytology Task Force.

Digital cytology and artificial intelligence (AI) are gaining greater adoption in the cytology laboratory. However, peer-reviewed real-world data and literature are lacking in regard to the current clinical landscape. The American Society of Cytopathology in conjunction with the International Academy of Cytology and the Digital Pathology Association established a special task force comprising 20 members with expertise and/or interest in digital cytology. The aim of the group was to investigate the feasibility of incorporating digital cytology, specifically cytology whole slide scanning and AI applications, into the workflow of the laboratory. In turn, the impact on cytopathologists, cytologists (cytotechnologists), and cytology departments were also assessed. The task force reviewed existing literature on digital cytology, conducted a worldwide survey, and held a virtual roundtable discussion on digital cytology and AI with multiple industry corporate representatives. This white paper, presented in 2 parts, summarizes the current state of digital cytology and AI practice in global cytology practice. Part 1 of the white paper is presented as a separate paper which details a review and best practice recommendations for incorporating digital cytology into practice. Part 2 of the white paper presented here provides a comprehensive review of AI in cytology practice along with best practice recommendations and legal considerations. Additionally, the cytology global survey results highlighting current AI practices by various laboratories, as well as current attitudes, are reported.

Vasculopathy and Increased Vascular Congestion in Fatal COVID-19 and Acute Respiratory Distress Syndrome.

Rationale: The leading cause of death in coronavirus disease 2019 (COVID-19) is severe pneumonia, with many patients developing acute respiratory distress syndrome (ARDS) and diffuse alveolar damage (DAD). Whether DAD in fatal COVID-19 is distinct from other causes of DAD remains unknown. Objective: To compare lung parenchymal and vascular alterations between patients with fatal COVID-19 pneumonia and other DAD-causing etiologies using a multidimensional approach. Methods: This autopsy cohort consisted of consecutive patients with COVID-19 pneumonia (n = 20) and with respiratory failure and histologic DAD (n = 21; non-COVID-19 viral and nonviral etiologies). Premortem chest computed tomography (CT) scans were evaluated for vascular changes. Postmortem lung tissues were compared using histopathological and computational analyses. Machine-learning-derived morphometric analysis of the microvasculature was performed, with a random forest classifier quantifying vascular congestion (CVasc) in different microscopic compartments. Respiratory mechanics and gas-exchange parameters were evaluated longitudinally in patients with ARDS. Measurements and Main Results: In premortem CT, patients with COVID-19 showed more dilated vasculature when all lung segments were evaluated (P = 0.001) compared with controls with DAD. Histopathology revealed vasculopathic changes, including hemangiomatosis-like changes (P = 0.043), thromboemboli (P = 0.0038), pulmonary infarcts (P = 0.047), and perivascular inflammation (P < 0.001). Generalized estimating equations revealed significant regional differences in the lung microarchitecture among all DAD-causing entities. COVID-19 showed a larger overall CVasc range (P = 0.002). Alveolar-septal congestion was associated with a significantly shorter time to death from symptom onset (P = 0.03), length of hospital stay (P = 0.02), and increased ventilatory ratio [an estimate for pulmonary dead space fraction (Vd); p = 0.043] in all cases of ARDS. Conclusions: Severe COVID-19 pneumonia is characterized by significant vasculopathy and aberrant alveolar-septal congestion. Our findings also highlight the role that vascular alterations may play in Vd and clinical outcomes in ARDS in general.

Initial experience with a homemade "hybrid-tome" for needle-knife precut in patients with difficult biliary cannulation.

Background and study aims Current clinical guidelines recommend needle-knife precut (NKP) as the primary and best method for performing a biliary cannulation (BC) when simple techniques fail and the criteria are met for difficult BC (DBC). However, many endoscopists avoid or defer early NKP in favor of alternative, simpler techniques that have not been shown to be either safer or more effective. Our goal is to test a device that provides the needle-knife papillotome (NKPT) with traction capability and which can facilitate the learning and execution of NKP. Patients and methods This was a descriptive bicentric observational study of a personal cohort of patients undergoing early NKP to analyse the efficacy and safety of the technique with a "hybrid-tome" (HT) built using the isolated core of a NKPT and a conventional canulotome. Results Over a 4-year period, we performed 43 NKPs with the HT, achieving BC in one or two steps in all cases. The 100 % technical success was matched by a 95 % clinical success rate. We recorded 11 adverse events (23 %): five hemorrhages, four pancreatitis, and two cholangitis. In addition to the objective data, we confirmed that HT facilitates alignment with the duodenal papilla and the execution of pre-cutting, especially if the papilla is intradiverticular or hidden by folds. Conclusions The HT tested seems to help trained endoscopists to perform NKP, especially in some anatomic situations, which can improve compliance with the guidelines recommended for early NKP in patients with DBC.

Digital Image Analysis for Estimating Stromal CD8+ Tumor-Infiltrating Lymphocytes in Lung Adenocarcinoma.

BACKGROUND: Stromal CD8+ tumor-infiltrating lymphocytes (TILs) are an important prognostic and predictive indicator in non-small cell lung cancer (NSCLC). In this study, we aimed to develop and test the feasibility of a digital image analysis (DIA) workflow for estimating stromal CD8+ TIL density. METHODS: A DIA workflow developed in a software platform (QuPath) was applied to a specified region of interest (ROI) within the stromal compartment of dual PD-L1/CD8 immunostained slides from 50 lung adenocarcinoma patients. A random tree classifier was trained from 25 training cases and applied to 25 test cases. The DIA-estimated CD8+ TIL densities were compared to manual estimates of three pathologists, who independently quantitated the percentage of CD8+ TILs from predefined ROIs in QuPath. RESULTS: The average estimated total stromal cell count per case was 520 (range: 282-816) by QuPath and 551 (range: 265-744) by pathologists. The DIA-estimated CD8+ TIL density (mean = 16.9%) was comparable to pathologists' manual estimates (mean = 15.9%). A paired t-test showed no statistically significant difference between DIA and pathologist estimates of CD8+ TIL density among both training (n = 25, P = 0.55) and test (n = 25, P = 0.34) cases. There was an almost perfect agreement between QuPath and each pathologist's estimates of CD8+ TIL density (κ = 0.85-0.86). CONCLUSIONS: These findings demonstrate the feasibility of applying a DIA workflow for estimating stromal CD8+ TIL density in NSCLC. DIA has the potential to provide an efficient and standardized approach for estimating stromal CD8+ TIL density.

Digital media archive for gross pathology images based on open-source tools and Fast Healthcare Interoperability Resources (FHIR).

Macroscopic examination of surgical pathology and autopsy cases is a fundamental component of anatomic pathology. The photographic documentation of such clinical specimens is essential, and it may be required in certain instances. Our department began using consumer-grade digital cameras in 2005 to improve the practice of gross photography. However, the lack of an application to correctly catalog the photographs resulted in thousands of digital image files scattered across shared network drives, with limited case and patient metadata, making image retrieval a cumbersome and sometimes impossible task. Thirteen years later, we examined the legacy method of acquiring and accessing gross photographs in our department and determined the need for a web-based digital media archive to capture images with structured metadata. Using several open-source tools, including MediaWiki, we developed a flexible platform for building our digital media archive with a data schema based on the Fast Healthcare Interoperability Resources standard. Following a short pilot, we replaced the legacy method of handling gross pathology images with a new acquisition workflow and digital media archive. Through March 2021, 233 distinct users have accessed the system, 58 of which have uploaded 21,024 images. Of those images, 13,684 (65.1%) correspond to surgical pathology images, 4045 (19.2%) belong to neuropathology cases, and 3295 (15.7%) originate from autopsies. We demonstrate the design and implementation of a customizable anatomic pathology digital media archive solution in an academic pathology department setting using a modern standard for exchanging healthcare information electronically. The system's efficiency and scalability for our current operation will enable us to integrate with other applications and pathology informatics initiatives in the future.

Rosai-Dorfman disease of the pancreas: Cytologic analysis of three cases presenting as pancreatic masses.

Rosai-Dorfman Disease (RDD), or sinus histiocytosis with massive lymphadenopathy, is a rare entity characterized by proliferating S100-positive histiocytes. It is most commonly found in lymph nodes with extranodal involvement usually occurring in the head and neck. Pancreatic involvement is extremely rare. The pathology department archives were searched for fine needle aspirations and pancreatic resections showing evidence of RDD. Clinicopathologic features, cytologic smears, cell blocks, immunocytochemical stains and surgical resections were reviewed. Three cases were identified. They were all females, aged 65, 69 and 75, with involvement of the pancreatic tail or head by solid masses of median size 2.3 cm (range 2.1-4.5 cm). Cytologic findings on smears included multiple histiocyte clusters resembling loosely cohesive epithelioid granulomas, singly dispersed histiocytes with moderate to marked nuclear atypia and characteristic emperipolesis. These atypical histiocytes stained positively for CD68, CD163 and S100. Smear background contained variable mixed inflammatory cells, necrotic debris and stromal fragments. The RDD diagnosis was further confirmed on pancreatic resection in two patients and core biopsy in one. The latter patient required three separate procedures before a definitive diagnosis was made. RDD of pancreas is a rare benign inflammatory condition that is diagnostically challenging on cytology. This can cause delays in cytologic diagnosis and/or misdiagnosis. Identification of characteristic cytologic features, primarily histiocytes with emperipolesis, and matching immunocytochemical profile can ensure accurate diagnosis and distinction from mimics.

Towards a "Net" generation of Pathologists: the pathCast online remote learning platform.

In recent years, digital and communication technology has been changing the way to spread knowledge in Medicine. In the field of Pathology, several remote learning resources have been made available through multiple social media platforms (Facebook, Twitter and others), YouTube channels and dedicated Websites, with a growing number of freely available lectures or tutorials, broadcasted live and/or archived for on-demand viewing. All these internet-based resources enable the pursuit of a flexible, independent, self-motivated and self-directed way of learning that fits perfectly with the increasing limitations of time, space and speed of modern day learners.These resources have played a significant role in filling the void of conventional education during the ongoing Covid-19 pandemic. Moreover, with their widespread diffusion throughout communities of Pathologists from all over the world they help to reduce the educational gap between resource-rich and resource-poor countries, having the potential to become standardized knowledge-sharing platforms and to be incorporated into curricula at any level.pathCast is one of the most robust and reliable open-access online remote learning platforms for pathologists, which live-streams lectures across the world. In the present paper we describe its structure, its acceptance by the global community of pathologists, what innovation elements has introduced regarding methodologies for education and its powerful and positive impact for residency training and continuing life-long education of practicing pathologists. A comprehensive list of the pathCast lectures with the respective links is also provided along with a brief discussion on other freely accessible online educational resources for pathologists.

#FNAFriday: How cytopathologists learn, teach, and share knowledge on Twitter.

BACKGROUND: Twitter is an expanding social media network among cytopathologists to share knowledge. Tweets are made up of text which may also include images or video. All tweets labeled under a hashtag can be tracked. The #FNAFriday hashtag was created in 2015 by one of the authors (X.J.) to build a community of individuals, to educate and share interesting cases, and highlight a variety of diagnoses with FNA specimens. METHODS: We retrospectively extracted all tweets labeled with #FNAFriday from April 2015 to mid-February 2019 (47 mo) using the Twitter search engine. The data point included: author, number of figures, type of cytology-stain, use of immunocytochemistry, histochemistry or molecular techniques, and the subspeciality. The educational content was categorized as: live-tweeting, training activities, and publication references. The number if comments, retweets and likes was also recorded. RESULTS: A total of 349 original tweets using #FNAFriday were tracked with an average of 7.43 tweets/month. We describe the "top three" countries with most tweets, active users and subspecialties. The most frequent stain was Papanicolau and part of the content of the tweets was using cellblock (14.04%), histologic correlation (10.03%), immunocytochemistry (8.60%), molecular tests (2.01%), gross pictures (4.58%), and radiologic pictures (3.4%). CONCLUSION: The presence of cytopathologists on Twitter who want to share their cases has increased. The weekly FNAFriday label with other cytology hashtags is a specific keyword for those interested in the field.

pathCast: An Interactive Medical Education Curriculum That Leverages Livestreaming on Facebook and YouTube.

PROBLEM: Global connectivity and awareness have significantly increased over the past 3 decades, yet medical education remains mostly unchanged in its delivery-local didactic teaching, supplemented with hands-on clinical experiences. APPROACH: Beginning in 2016, the authors leveraged the livestreaming capabilities of Facebook and YouTube to create a platform called pathCast to broadcast pathology lectures to an international community of medical professionals. An interactive pathology curriculum was designed to address challenging topics across various subspecialties. Expert pathologists were invited to deliver 60-minute lectures using digital or glass slides or traditional slide decks. Remote (online) attendees interacted with lecturers in real time using the broadcasts' chat interface. Facebook's and YouTube's analytics were evaluated to assess the performance of all lectures. OUTCOMES: From June 2016 to December 4, 2019, 53 speakers delivered 87 lectures representing 18 pathology subspecialties in 9 different languages (with 78 [89.7%] in English only) and from various geographic regions. The lectures hosted on the Facebook channel have garnered 8,333 followers and 52,171 views for a total of 386,200 minutes of watch time, and the lectures hosted on the YouTube channel have accumulated 5,891 subscribers and 292,735 views for a total of 50,674 hours of watch time. The lectures have been viewed by users from 1,093 unique cities across 124 countries. NEXT STEPS: The authors will continue to develop the curriculum to further disseminate pathology education on a global scale.

Milan Interobserver Reproducibility Study (MIRST): Milan System 2018.

INTRODUCTION: Prior to the 2018 publication of the Milan System for Reporting Salivary Gland Cytopathology (MSRSGC), a Web-based interobserver study was performed to evaluate MSRSGC reporting categories, identify cytomorphologic features that represent poor sources of agreement, and establish a baseline for future studies. MATERIAL AND METHODS: Study participants evaluated 75 images chosen from the MSRSGC image set, prior to the release of the Milan Atlas. Images spanned all diagnostic categories including typical and borderline cytomorphology. Participant demographics were collected on level of training, practice patterns, and experience. RESULTS: A total of 647 persons attempted access to the survey. Of these, 555 correctly answered the qualifying questions. Participants included: 16.5% ASCP Certified Cytotechnologists, 2.8% Specialist Cytotechnologists, 5.8% IAC Certified individuals, 14.3% Anatomic (AP) Certified Pathologists, 38.9% AP and Cytopathology Certified Pathologists, and 15.3% pathology trainees. Length of participant practice varied from 0 to 54 years. In our sample, 43.4% of participants came from academic centers, 17.6% from private hospitals; and 13.3% from commercial/private laboratories. Overall, 42% of respondents agreed with the reference interpretations of salivary gland lesions. The best agreement was seen in cytopathology certified pathologists. Among the MSRSGC categories, best agreement was found in Neoplasm-Benign (58.9%) and Non-Diagnostic (49.2%) categories, followed by Malignant (48.4%). The agreement rates for Salivary Gland Lesion of Uncertain Malignant Potential (SUMP) and Suspicious For Malignancy (SFM) were 23.6% and 22.7%, respectively. CONCLUSIONS: Similar to the reproducibility studies conducted for gynecologic and urinary cytopathology, the most important factor in diagnostic reproducibility was a priori classification of image difficulty, although people with higher certifications performed better.

Rosai-Dorfman Disease of the Pancreas Shows Significant Histologic Overlap With IgG4-related Disease.

Rosai-Dorfman disease (RDD) is a rare entity characterized by proliferating S100-positive histiocytes. Originally described in lymph nodes, it can involve extranodal sites. Pancreatic involvement is rare, with <10 cases previously reported. Recent studies demonstrate a possible overlap between RDD and the more common IgG4-related disease (IRD), which could further complicate pathologic diagnosis. We describe distinct morphologic characteristics as well as overlapping histologic features of IRD in 5 cases of pancreatic RDD at our institution and compare these to a cohort of nonpancreatic extranodal RDD cases. All pancreatic cases were mass forming and had spindled patterns of elongated histiocytes with smaller areas of more classical appearing RDD; all cases had areas of storiform fibrosis and dense lymphoplasmacytic infiltrates with no increase in IgG4-positive plasma cells, and all cases had some degree of vasculitis (4 cases had obliterative vasculitis). Thirteen nonpancreatic extranodal RDD cases had dense lymphoplasmacytic infiltrates; most (85%) had some fibrosis with 46% showing storiform fibrosis, 85% had vasculitis with 31% demonstrating obliterative vasculitis and 2 cases had increased IgG4 staining. Extranodal (pancreatic and nonpancreatic) RDD often shows overlapping morphologic features with IRD, including lymphoplasmacytic inflammation, storiform fibrosis with elongated histiocytes and vasculitis. This can create a diagnostic challenge in the pancreas where IRD is more commonly encountered. Pathologists need to be aware that RDD can occur in the pancreas and should include RDD in the differential of any mass forming pancreatic lesion in which morphologic features of IRD are present.