Genomic Profiling of Rare Undifferentiated Sarcomatoid Subtypes of Pancreatic Carcinomas: In Search of Therapeutic Targets.

PURPOSE: The highly aggressive undifferentiated sarcomatoid carcinoma (USC) subtype of pancreatic ductal adenocarcinoma (PDAC) remains poorly characterized because of its rarity. Previous case reports suggest that immune checkpoint inhibitors could be a promising treatment strategy, but the prevalence of established predictive biomarkers of response is largely unknown. The objective of this study was to leverage comprehensive genomic profiling of USC PDAC tumors to determine the prevalence of biomarkers associated with potential response to targeted therapies. METHODS: USC tumors (n = 20) underwent central pathology review by a board-certified gastrointestinal pathologist to confirm the diagnosis. These samples were compared with non-USC PDAC tumors (N = 5,562). Retrospective analysis of DNA and RNA next-generation sequencing data was performed. RESULTS: USC PDACs were more frequently PD-L1+ by immunohistochemistry than non-USC PDAC (63% v 16%, respectively, P < .001). Furthermore, USC PDAC had an increase in neutrophils (8.99% v 5.55%, P = .005) and dendritic cells (1.08% v 0.00%, q = 0.022) and an increased expression of PDCD1LG2 (4.6% v 1.3%, q = 0.001), PDCD1 (2.0% v 0.8%, q = 0.060), and HAVCR2 (45.9% v 21.7%, q = 0.107) than non-USC PDAC. Similar to non-USC PDAC, KRAS was the most commonly mutated gene (86% v 90%, respectively, P = 1). CONCLUSION: To our knowledge, this work represents the largest molecular analysis of USC tumors to date and showed an increased expression of immune checkpoint genes in USC tumors. These findings provide evidence for further investigation into immune checkpoint inhibitors in USC tumors.

In Search of Nodular Gastric Antral Vascular Ectasia: A Distinct Entity or Simply Hyperplastic Polyps Arising in Gastric Antral Vascular Ectasia?

CONTEXT.­: Nodular gastric antral vascular ectasia (GAVE) is a reported phenotype of GAVE that has histologic features overlapping with gastric hyperplastic polyps (GHPs), with additional features often seen in flat mucosa of GAVE. OBJECTIVE.­: To determine if nodular GAVE and GHPs are distinct lesions by evaluating the prevalence of features reported in nodular GAVE in GHPs with or without associated GAVE. DESIGN.­: A review of all lesions diagnosed as GHPs between 2014 and 2017 was performed. Slides were analyzed for a number of features including established histologic features of GAVE without knowledge of clinical or endoscopic features. RESULTS.­: A total of 90 polyps were analyzed including 18 from patients with GAVE (20%). GAVE polyps were larger than non-GAVE polyps (average size, 1.3 cm versus 0.68 cm; P < .001), with more common extensive ulceration and associated granulation tissue (61.11% [n = 11] versus 4.17% [n = 3]; P = .004), fibrin thrombi (50% [n = 9] versus 15% [n = 11]; P = .003), moderate to marked vascular ectasia (83% [n = 15] versus 35% [n = 11]; P = .001), and fibrohyalinosis (72% [n = 13] versus 28% [n = 20]; P = .001). All polyps showed foveolar hyperplasia and smooth muscle proliferation. There were no features that were exclusively found in GAVE or non-GAVE cases. CONCLUSIONS.­: Nodular GAVE appears to represent GHPs arising in a background of GAVE, with superimposed features found in flat mucosa of GAVE stomachs. The presence of fibrin thrombi, marked vascular ectasia, fibrohyalinosis, and/or ulceration in a GHP is suggestive but not diagnostic of GAVE, and the absence of these features does not rule out GAVE.

Primary Pancreatic Liposarcoma: An Unexpected Cause of a Pancreatic Mass.

Liposarcoma is the most common type of soft-tissue sarcoma and typically occurs in the extremities or retroperitoneum. Primary liposarcoma of the pancreas is exceedingly rare, with only 10 cases reported since 1979. We present a patient who was incidentally discovered to have a pancreatic mass on imaging, which was ultimately diagnosed as dedifferentiated pancreatic liposarcoma. We review the clinical and histologic features of pancreatic liposarcoma in this case and in the 10 previously reported cases to increase awareness and knowledge of this rare disease.

Transposon delivery for CRISPR-based loss-of-function screen in mice identifies NF2 as a cooperating gene involved with the canonical WNT signaling molecular class of hepatocellular carcinoma.

Various molecular subclasses of hepatocellular carcinoma (HCC) exists, with many novel cooperating oncogenes and tumor suppressor genes involved in its tumorigenesis. The emerging importance of WNT signaling in HCC has been established. However, the intricate genetic mechanisms involved in this complex signaling pathway remains to be elucidated. Importantly, while some cooperating genes have been identified, there are still many unknown genes associated with catenin beta 1 (CTNNB1)-induced HCC. Mutations in both oncogenes and tumor suppressor genes are required for HCC tumorigenesis. The emergence of the CRISPR/Cas9 system has allowed researchers now to target both alleles efficiently. In this novel study, the Sleeping Beauty transposon system was used as a gene delivery system in vivo to stably integrate an expression cassette that carry pools of gRNAs and overexpress a mutant version of CTNNB1 into the hepatocyte genome. We identified 206 candidate genes that drive HCC tumorigenesis in the context of WNT signaling activation and, neurofibromin 2 (NF2) gene, a known tumor suppressor gene with clinical relevance was validated in this proof-of-principle study.

Novel Sequence of Endoscopic Therapy for the Management of Colonic Adenocarcinoma and Surrounding Adenoma.

An 80-year-old man with a history of an orthotopic heart transplant was found to have a 25 × 40 mm centrally ulcerated mass at the hepatic flexure during evaluation of anemia. Owing to comorbidities, the patient was deemed to be a poor surgical candidate and was referred to the advanced endoscopy team to explore palliative and potentially curative options. We present a novel sequence of intervention involving full-thickness resection with subsequent morcellation clean-up to achieve complete endoscopic removal of a neoplastic lesion.

Disseminated Blastomycosis Mimicking Metastatic Head and Neck Cancer in a 70-year-Old Man.

Blastomycosis is a fungal infection known to mimic many disease processes, including malignancy. A 70-year-old man presented with an enlarging neck mass and, incidentally found on preliminary imaging, a lung mass. The initial biopsy of the neck mass demonstrating cytologic atypia and mitotic figures was suggestive of malignancy. Whole body positron emission tomography (PET)/CT revealed hypermetabolic lesions in multiple sites, including the neck, lung, and soft tissue, raising concern for metastatic disease. Repeat sampling from multiple lesions, however, demonstrated granuloma. Microbiological studies were collected, and Blastomyces dermatitidis was isolated in culture. The diagnosis of disseminated blastomycosis was made, and the patient received antifungal therapy with good response. A high degree of suspicion for blastomycosis in endemic areas is required to ensure patients receive appropriate and timely treatment. Laryngoscope, 133:2237-2239, 2023.

Efficacy and Safety of Ceritinib 450 mg/day with Food and 750 mg/day in Fasted State in Treatment-Naïve Patients with ALK+ Non-Small Cell Lung Cancer: Results from the ASCEND-8 Asian Subgroup Analysis.

PURPOSE: Previous report from the ASCEND-8 trial showed consistent efficacy with less gastrointestinal (GI) toxicity in patients with anaplastic lymphoma kinase-rearranged (ALK+) advanced/metastatic non-small cell lung cancer (NSCLC) treated with ceritinib 450-mg with food compared with 750-mg fasted. In this subgroup analysis, we report outcomes in Asian patients of the ASCEND-8 trial. MATERIALS AND METHODS: Key efficacy endpoints were blinded independent review committee (BIRC)-assessed overall response rate (ORR) and duration of response (DOR) evaluated per Response Evaluation Criteria in Solid Tumors v1.1. Other efficacy endpoints were investigator-assessed ORR and DOR; BIRC- and investigator-assessed progression-free survival (PFS) and disease control rate; overall survival (OS). Safety was evaluated by frequency and severity of adverse events. RESULTS: At final data cutoff (6 March 2020), 198 treatment-naïve patients were included in efficacy analysis, of which 74 (37%) comprised the Asian subset; 450-mg fed (n=29), 600-mg fed (n=19), and 750-mg fasted (n=26). Baseline characteristics were mostly comparable across study arms. At baseline, more patients in 450-mg fed arm (44.8%) had brain metastases than in 750-mg fasted arm (26.9%). Per BIRC, patients in the 450-mg fed arm had a numerically higher ORR, 24-month DOR rate and 24-month PFS rate than the 750-mg fasted arm. The 36-month OS rate was 93.1% in 450-mg fed arm and 70.9% in 750-mg fasted arm. Any-grade GI toxicity occurred in 82.8% and 96.2% of patients in the 450-mg fed and 750-mg fasted arms, respectively. CONCLUSION: Asian patients with ALK+ advanced/metastatic NSCLC treated with ceritinib 450-mg fed showed numerically higher efficacy and lower GI toxicity than 750-mg fasted patients.

Trends in the Incidence of Cancer Among Adolescent and Young Adults in Alberta, 1983-2017: A Population-Based Study Using Cancer Registry Data.

Purpose: To describe the cancer incidence burden and trends among adolescent and young adults (AYAs) in Alberta, Canada over a 35-year period. Methods: We obtained data from the Alberta Cancer Registry on all first primary cancers, excluding non-melanoma skin cancer, diagnosed at ages 15-39 years among residents in Alberta from 1983 to 2017. Cancers were classified by using Barr's AYA cancer classification system. Age-standardized incidence rates (ASIR) and the average annual percentage change (AAPC) in incidence rates were calculated. Statistically significant changes in the AAPC during the study period were assessed using Joinpoint regression. Results: Overall, 23,652 incident cases of AYA cancer were diagnosed in Alberta. Females accounted for ∼60% of the diagnoses. AYA cancer increased significantly over the study period overall (AAPC: 0.5%; 95%CI: 0.3%-0.7%), for each sex (AAPCmale: 0.7%; 95%CI: 0.4%-0.9%; AAPCfemale: 0.4%; 95%CI: 0.2%-0.6%), and among male and female 20-39 year-olds. Although statistically significant increases were observed in 11 out of 29 cancer sites for at least a portion of the study period, with significant AAPCs ranging from 0.8% (95%CI: 0.01%-1.5%) to 6.6% (95%CI: 4.6%-8.5%), the main driver was thyroid cancer (AAPC: 3.7%; 95%CI: 3.2%-4.2%). Statistically significant decreases were observed for six cancer sites, with AAPCs ranging from -6.4% (95%CI: -8.7% to -4.1%) to -1.1% (95%CI: -1.8% to -0.5%). Conclusions: There is a growing cancer burden among AYAs in Alberta, which is driven primarily by thyroid cancer and early-onset cancers in males. These results highlight the need for etiological studies and tertiary strategies to prevent and mitigate morbidity and mortality in the AYA population.

Mixed neuroendocrine/Non-neuroendocrine neoplasm (MiNEN) of gastrointestinal lineage arising in an ovarian mature cystic teratoma.

•Mixed neuroendocrine/non-neuroendocrine neoplasm (MiNEN) of gastrointestinal lineage arising in an ovarian mature cystic teratoma is extremely rare.•It is important to differentiate the gastrointestinal-type adenocarcinoma arising along with neuroendocrine tumor from a primary mucinous adenocarcinoma of the ovary. SATB2 and CDX2 Immunohistochemical stains play important role in differentiate these two.•This case highlights the careful morphologic evaluation and extensive sampling is crucial to make this rare diagnosis.

Evaluation of abnormal gallbladder imaging findings: Surgical management and pathologic correlations in early-stage gallbladder cancer.

Gallbladder cancer is a rare but potentially fatal disease. It is often asymptomatic in early stages and is frequently found incidentally or during the workup for benign biliary disease. We present two patients who each had suspicious gallbladder imaging findings and highlight their differences on radiologic and pathologic examination.

Genomic characterization of undifferentiated sarcomatoid carcinoma of the pancreas.

Undifferentiated sarcomatoid carcinoma (USC) of the pancreas is a rare but especially aggressive variant of pancreatic ductal adenocarcinoma (PDAC), composed of at least 80% of sarcomatoid cells. This study aimed to elucidate its clinicopathological and molecular features. The study cohort included 10 patients with pancreatic USC. Clinicopathological parameters were determined for each patient. The molecular profile was investigated using next-generation sequencing (NGS). Histologically, all tumors were hypercellular neoplasms with spindle-shaped or sarcomatoid cells. All patients showed vascular and perineural invasion. Most patients had a poor prognosis. NGS showed important similarities with conventional PDAC, including frequent alterations in the classic PDAC drivers, KRAS (100% of cases), TP53 (90%), and CDKN2A (60%). There were also some important distinctions from conventional PDAC: 1) SMAD4, a typical PDAC driver gene, was mutated in only one case (10%); 2) Another distinctive molecular feature was the recurrent KRAS amplification (30% of cases), which is very rare in conventional PDAC. It has been previously reported in another subtype of pancreatic undifferentiated carcinoma, the rhabdoid variant, and may be a key event leading to the acquisition of an undifferentiated phenotype in a subgroup of cases; 3) Lastly, in two different cases, we detected two potentially actionable targets, not belonging to the typical PDAC molecular landscape, such as MCL1 amplification and POLQ mutation. Our study sheds light on this rare tumor type, which shows aggressive biological behavior and few druggable alterations. The most distinctive molecular features of pancreatic USC are the paucity of SMAD4 alterations and recurrent KRAS amplification.

Effects of COVID-19 pandemic on cytology: specimen adequacy in fine-needle aspiration of palpable head and neck masses.

INTRODUCTION: At our institution, palpation-guided fine-needle aspiration (FNA) is performed by the cytopathology service on an outpatient basis at the request of otolaryngologist surgeons. The aim of this study is to assess the effect of COVID lockdown measures on our FNA service with specific focus on adequacy rates. MATERIALS AND METHODS: All palpation-guided FNA performed in 2019 to 2020 were identified in our pathology database. Adequacy rates were compared for 3 time periods in 2020: pre-COVID, lockdown, and post-lockdown. RESULTS: In 2019, 121 FNAs were performed with 98% (119 of 121) obtained by pathology and only 2% (2 of 121) obtained by surgeons. In 2020, 89 FNAs were performed with 45% (40 of 89) collected by pathologists and 55% (49 of 89) by surgeons. During the pre-COVID period of 2020, 27 FNAs were collected, 85% (23 of 27) by pathologists, 8.7% of these (2 of 23) were nondiagnostic. Of the 4 FNAs performed by surgeons, all were positive for malignancy. During COVID lockdown all 24 FNAs were performed by surgeons with a 50% (12 of 24) nondiagnostic rate. Post-lockdown, with FNA referrals still below pre-COVID levels, surgeons performed 55.3% (21 of 38) of FNAs with 28.6% (6 of 21) non-diagnostic, while pathology performed 44.7% (17 of 38) with an 11.8% (2 of 17) nondiagnostic rate. CONCLUSIONS: Our FNA service noted significant changes in 2020 as a result of the COVID pandemic. Nondiagnostic rates were significantly increased in 2020 compared with 2019, primarily due to a shift to majority surgeon-performed palpation-guided FNA in the absence of cytopathology service during the lockdown period.

Average lifespan shortened due to Hodgkin lymphoma, non-Hodgkin lymphoma, multiple myeloma, and leukemia in Japan, 1990-2015.

We examined whether there were gains in lifespan among patients who died from hematological cancers in Japan between 1990 and 2015 using the novel average lifespan shortened (ALSS) measure. We obtained mortality data from the World Health Organization mortality database. Years of life lost (YLL) was calculated using Japanese life tables. ALSS measure was calculated as a ratio of YLL to the expected lifespan. The ALSS results showed that the lifespan of patients who died from hematological cancers has improved over time. For instance, women who died of leukemia in 1990 lost about 34% of their lifespan; conversely, those who died in 2015 lost about 20%. Likewise, men dying from non-Hodgkin lymphoma lost about 22% of their lifespan in 1990, whereas men lost about 14% in 2015. In summary, the new ALSS measure shows prolonged lifespans among patients who died from hematological cancers in Japan over the study period.

Exploration of INSM1 and hASH1 as additional markers in lung cytology samples of high-grade neuroendocrine carcinoma with indeterminate neuroendocrine differentiation.

BACKGROUND: Traditional neuroendocrine (NE) markers synaptophysin, chromogranin, and CD56 play an integral role in affirming the diagnosis of high-grade lung NE carcinoma, however promising markers, INSM1, and hASH1, have been identified. We investigated the utility of these markers in pulmonary cytology specimens, particularly in cases where results of traditional NE markers were equivocal. METHODS: A retrospective search of cytology cases obtained via endobronchial ultrasound (EBUS)-guided FNA revealed 26 cases of high-grade lung carcinoma where an indeterminate diagnosis of small-cell lung carcinoma (SCLC) was based on equivocal IHC staining with traditional NE markers. A separate cohort of 23 cases positive for all traditional markers with a definitive diagnosis of SCLC was also selected. Cytology cellblock sections were immunostained with INSM1 and hASH1 and analyzed using H-score methodology (score range 0-300). A score of ≥95 was considered "positive." RESULTS: INSM1 was positive in 19/24 (79.2%) of cases of high-grade lung carcinoma with indeterminate NE differentiation, while hASH1 was positive in 6/24 (25.0%). Chromogranin was seen only focally positive (<10% of cells) in 4/24 (16.7%), synaptophysin positive in 16/24 (66.7%), and CD56 positive in 14/21 (66.7%). Among unambiguous cases, INSM1 was positive in all cases with an average score of 233.9, while hASH1 was positive in 21/23 (91.3%) with an average score of 196.3. CONCLUSION: Compared with traditional NE stains and to hASH1, INSM1 was expressed in a higher number of cases of high-grade lung NE carcinomas in cytology cellblock specimens, making it a superior, more sensitive NE marker.

ZBTB20 regulates WNT/CTNNB1 signalling pathway by suppressing PPARG during hepatocellular carcinoma tumourigenesis.

BACKGROUND & AIMS: Zinc finger and BTB domain containing 20 (ZBTB20) has been implicated as a potential oncogene in liver cancer. However, knockout studies have shown it to be a transcriptional repressor of the alpha-foetoprotein (Afp) gene in adult liver, and reduced levels of ZBTB20 allow for upregulation of AFP with increased tumour severity in certain cases of hepatocellular carcinoma (HCC). As there are many discrepancies in the literature regarding its role in liver tumourigenesis, the aim of this study was to elucidate the role of ZBTB20 in HCC tumourigenesis. METHODS: A reverse genetic study using the Sleeping Beauty (SB) transposon system in mice was performed to elucidate the role of ZBTB20 in HCC tumourigenesis. In vitro ZBTB20 gain- and loss-of-function experiments were used to assess the relationship amongst ZBTB20, peroxisome proliferator activated receptor gamma (PPARG) and catenin beta 1 (CTNNB1). RESULTS: Transgenic overexpression of ZBTB20 in hepatocytes and in the context of transformation related protein (T r p53) inactivation induced hepatic hypertrophy, activation of WNT/CTNNB1 signalling, and development of liver tumours. In vitro overexpression and knockout experiments using CRISPR/Cas9 demonstrated the important role for ZBTB20 in downregulating PPARG, resulting in activation of the WNT/CTNNB1 signalling pathway and its downstream effectors in HCC tumourigenesis. CONCLUSIONS: These findings demonstrate a novel interaction between ZBTB20 and PPARG, which leads to activation of the WNT/CTNNB1 signalling pathway in HCC tumourigenesis. LAY SUMMARY: ZBTB20 has been implicated as a potential oncogene in liver cancer. Herein, we uncover its important role in liver cancer development. We show that it interacts with PPARG to upregulate the WNT/CTNNB1 signalling pathway, leading to tumourigenesis.

Designing and Implementing a Virtual Anatomic Pathology Elective During the COVID-19 Pandemic.

The COVID-19 pandemic transformed conventional undergraduate medical education, converting previously in-person clerkships into virtual experiences. In order to allow students to gain exposure to the field of pathology, make connections with pathologists, and provide opportunities for letters of recommendation, the authors quickly developed a Virtual Anatomic Pathology Elective at the University of Minnesota. We succeeded in developing the foundation of a Virtual Anatomic Pathology Elective that allows for the rotation to be accessible not only to our medical students but also to international medical graduates and medical students from different programs. In 1 month, we were able to create a 4-week elective that was available before the start of the 2021 residency application season. We provided students with the closest possible experience to an in-person Anatomic Pathology Elective by developing an introductory week of lectures and assignments that provided structure for the rotation, introduced the field of anatomic pathology, and demonstrated the role of pathologists in health care. Furthermore, students attended virtual resident lectures and grand rounds, participated in virtual sign-out sessions, and presented an interesting case to the faculty at the end of their rotation. The goal was ultimately to customize the curriculum to students' interests by making the rotation applicable to those applying to pathology as well as to other specialties (eg, general surgery, internal medicine, dermatology). Overall, we were able to design and implement a novel Virtual Anatomic Pathology Elective which we know can be effectively reproduced by other medical schools.

A rare sporadic pancreatic desmoid fibromatosis diagnosed by endoscopic ultrasound-guided fine-needle aspiration: Case report and literature review.

Intra-abdominal desmoid fibromatosis (also known as desmoid tumor) is a rare benign but often locally aggressive infiltrative fibrous proliferation. Pancreatic desmoid fibromatosis is even rarer, with only 31 cases previously reported in the English-language literature. These tumors present a distinct diagnostic challenge due to their rarity and non-specific image findings and presentation, with most cases diagnosed as desmoid fibromatosis only after surgical resection. This report presents a rare case of pancreatic desmoid fibromatosis in a 72 year old man, who on a follow-up CT for a previously diagnosed angiomyolipoma of the kidney was found to have a 4.0 cm pancreatic tail mass. This was sampled pre-operatively by endoscopic ultrasound (EUS)-guided fine-needle aspiration (FNA). Examination of the cytology material showed a low-grade spindle cell lesion. Immunohistochemistry (IHC) performed on FNA cell block showed the lesional cells to be positive for beta-catenin, consistent with fibromatosis. Additional mutational analysis on cell block material revealed the characteristic CTNNB1 gene mutation (T41A), confirming the diagnosis. The mass was then surgically resected and again confirmed to be desmoid fibromatosis on histopathologic examination. On review of previously published cases of pancreatic desmoid fibromatosis, most were initially suspected to be some type of pancreatic neoplasm and were not biopsied prior to surgical resection. This case suggests a potential key role for fine-needle aspiration cytology in the preoperative diagnosis of pancreatic and other intra-abdominal desmoid tumors, particularly as evidence emerges that non-surgical treatment may be a viable first option for some cases.

Evaluation and Comparison of Performance Parameters and Impact of Telepathology and Operator Experience on Endobronchial and Endoscopic Ultrasound-Guided Fine-Needle Aspiration.

OBJECTIVES: Endobronchial ultrasound- and endoscopic ultrasound-guided fine-needle aspiration (EBUS-/EUS-FNA) are minimally invasive techniques of diagnosing and staging malignancies. The procedures are difficult to master, requiring specific feedback for optimizing yield. METHODS: Over 2 years, EBUS-/EUS-FNA cases were gathered using the institutional pathology database. Patient and specimen characteristics were collected from the pathology database and electronic medical record. RESULTS: In 2 years, 789 unique FNA specimens were collected (356 EBUS and 433 EUS specimens). The cohort and each subgroup had excellent performance, which was enhanced by telepathology. The discrepancy rate was satisfactorily low. Hematolymphoid neoplasms are overrepresented in discrepant EBUS cases. The malignancy rates of cytology diagnostic categories were comparable to the literature. CONCLUSIONS: Using diagnostic yield and concordance results allow for comprehensive evaluation of the entire process of EBUS-/EUS-FNAs. This study's findings can influence patient management, training methods, and interpretation of results, while also acting as a model for others to investigate their own sources of inadequacy, discrepancy, and training gaps.

Performance of Ventana SP263 PD-L1 assay in endobronchial ultrasound guided-fine-needle aspiration derived non-small-cell lung carcinoma samples.

BACKGROUND: Introduction of programmed death-ligand 1 (PD-L1) inhibitors has significantly changed the treatment landscape of non-small-cell lung carcinomas (NSCLC). Since endobronchial ultrasound guided fine-needle aspiration (EBUS FNA) has become the primary diagnostic and staging modality for NSCLC, this study was pursued to determine the adequacy of Ventana SP263 PD-L1 assay in cytology cell blocks. DESIGN: Fifty NSCLC cases with cytology and corresponding histology specimens obtained between 2014 and 2018 were identified. After assessing for adequacy (100 or more tumor cells), forty cases were selected for Ventana SP263 PD-L1 immunohistochemistry (IHC) assay and assessed for tumor proportion scores (TPS) and staining intensity scores (SIS) and analyzed for concordance. RESULTS: Of the 40 matched pairs 33 (82.5%) showed concordant PD-L1 expression. On cytology, 32 cases were positive (8 high-expressors and 24 low-expressors) of which 27 were concordant and 5 discordant with matched histology specimens. On histology, 29 cases were positive (7 high-expressor and 22 low-expressors) while 11 cases were negative for PD-L1 expression of which 6 had concordant negative cytology. The intraclass correlation coefficients (ICC) for TPS was 0.81 with 95% confidence interval (0.68, 0.9) and for the SIS, it was 0.78 with 95% CI (0.62, 0.88), both considered as having excellent agreement. CONCLUSION: With an overall concordance rate of 82.5% between cytology and histology specimen, this study demonstrates the feasibility of PD-L1 IHC with SP263 clone on cytology samples of NSCLC and adds to a growing body of evidence validating the use of cytology cell blocks for PD-L1 expression testing.