Interobserver variability in cytopathology: How much do we agree?

Interobserver variability remains a major challenge for cytopathologists despite the development of standardized reporting and classification systems. Indeed, whereas moderate-to-good interobserver agreement is generally achievable when the differential diagnosis between benign and malignant entities is straightforward, high levels of variability make the diagnostic interpretation of atypical and suspicious samples not consistent. This review explores the landscape of interobserver agreement in cytopathology across different anatomical sites.

Molecular testing in salivary gland cytopathology: A practical overview in conjunction with the Milan system.

Recently, significant advances in the molecular characterization of salivary gland neoplasms have facilitated the classification and diagnosis of specific diagnostic entities. In the highly challenging diagnostic scenario of salivary malignancies, molecular testing is increasingly being adopted in routine practice to refine the cytological diagnosis of salivary lesions. Here, we reviewed the most recent evidence in the field of salivary glands molecular cytopathology.

Liquid biopsy: A promising tool for driving strategies and predicting failures in patients with classic Hodgkin lymphoma.

Classic Hodgkin lymphoma (cHL) consists of a heterogeneous group of haematological disorders that covers undifferentiated B cell neoplasms originating from germinal centre B cells. The HL molecular characterization still represents an ongoing challenge due to the low fraction of tumour Hodgkin and Reed-Sternberg cells mixed with a plethora of non-tumour haematological cells. In this scenario, next generation sequencing of liquid biopsy samples is emerging as a useful tool in HL patients' management. In this review, we aimed to overview the clinical and methodological topics regarding the implementation of molecular analysis in cHL, focusing on the role of liquid biopsy in diagnosis, follow-up, and response prediction.

Delphi expert consensus for whole slide imaging in thyroid cytopathology.

OBJECTIVE: Despite an increase in thyroid fine needle aspiration (FNA) and advances in whole slide imaging (WSI) adoption, digital pathology is still considered inadequate for primary diagnosis of these cases. Herein, we aim to validate the utility of WSI in thyroid FNAs employing the Delphi method strategy. METHODS: A panel of experts from seven reference cytology centres was recruited. The study consisted of two consecutive rounds: (1) an open-ended, free-response questionnaire generating a list of survey items; and (2) a consensus analysis of 80 selected shared WSIs from 80 cases by six investigators answering six morphological questions utilising a 1 to 5 Likert scale. RESULTS: High consensus was achieved for all parameters, with an overall average score of 4.27. The broad majority of items (84%) were ranked either 4 or 5 by each physician. Two badly scanned cases were responsible for more than half of the low-ranked (≤2) values (57%). Good to excellent (≥3) diagnostic confidence was reached in more than 95.2% of cases. For most cases (78%) WSI assessment was not limited by technical issues linked to the image acquisition process. CONCLUSION: This systematic Delphi study indicates broad consensus among participating physicians on the application of DP to thyroid cytopathology, supporting expert opinion that WSI is reliable and safe for primary diagnostic purposes.

Evaluating local thyroid cytopathology practices by molecular quality metrics: A multi-institutional study on 4651 FNAs with a focus on the role of the interventional cytopathologist.

BACKGROUND: The diagnostic accuracy of thyroid fine-needle aspiration (FNA) can be highly influenced by the technical skills of the operator performing the procedure and by interobserver variability in microscopic interpretation. This is particularly true for the indeterminate categories. Recently, molecular testing has been proposed as an ancillary tool for monitoring the performance of different thyroid cytopathology practices. The objective of this multicenter study was to evaluate the quality of different local cytopathology practices by assessing the impact of interventional cytopathologists on FNA adequacy for molecular testing and the variations in mutation rates across different health care centers operating in the Campania region. METHODS: The study included 4651 thyroid FNA samples diagnosed in different Southern Italian clinical laboratories belonging to the TIRNET (the Tiroide Network). FNA samples were collected by different proceduralists and were classified by local cytopathologists according to The Bethesda System for Reporting Thyroid Cytopathology. FNAs classified as atypia of undetermined significance, follicular neoplasm, suspicious for malignancy, and malignant were centralized for a real-time polymerase chain reaction-based, seven-gene test at the authors' institution. RESULTS: Centers that employed interventional cytopathologists obtained fewer unsatisfactory FNA samples for molecular testing (11.3%) than centers that employed noncytopathologists (16.7%; p < .05). Furthermore, a significant variation in the mutation rate was observed in FNAs diagnosed by different local cytopathologists; indeterminate categories had the highest percentage of mutation rate variability among centers. CONCLUSIONS: Interventional cytopathologists obtained higher yields of diagnostic material for molecular testing. Finally, the current results suggest that the variability in mutation rates among different centers may highlight the low reproducibility of microscopic criteria among cytopathologists, particularly for indeterminate cases.

Digital Examination of LYmph node CYtopathology Using the Sydney system (DELYCYUS): An international, multi-institutional study.

BACKGROUND: After a series of standardized reporting systems in cytopathology, the Sydney system was recently introduced to address the need for reproducibility and standardization in lymph node cytopathology. Since then, the risk of malignancy for the categories of the Sydney system has been explored by several studies, but no studies have yet examined the interobserver reproducibility of the Sydney system. METHODS: The authors assessed interobserver reproducibility of the Sydney system on 85 lymph node fine-needle aspiration cytology cases reviewed by 15 cytopathologists from 12 institutions in eight different countries, resulting in 1275 diagnoses. In total, 186 slides stained with Diff-Quik, Papanicolaou, and immunocytochemistry were scanned. A subset of the cases included clinical data and results from ultrasound examinations, flow cytometry immunophenotyping, and fluorescence in situ hybridization analysis. The study participants assessed the cases digitally using whole-slide images. RESULTS: Overall, the authors observed an almost perfect agreement of cytopathologists with the ground truth (median weighted Cohen κ = 0.887; interquartile range, κ = 0.210) and moderate overall interobserver concordance (Fleiss κ = 0.476). There was substantial agreement for the inadequate and malignant categories (κ = 0.794 and κ = 0.729, respectively), moderate agreement for the benign category (κ = 0.490), and very slight agreement for the suspicious (κ = 0.104) and atypical (κ = 0.075) categories. CONCLUSIONS: The Sydney system for reporting lymph node cytopathology shows adequate interobserver concordance. Digital microscopy is an adequate means to assess lymph node cytopathology specimens.

Ultrasonography-guided core-needle biopsy of lymphadenopathies suspected of lymphoma: Analysis on diagnostic efficacy and safety of 1000 front-line biopsies in a multicenter Italian study.

The reliability and safety of front-line ultrasonography guided core needle biopsy (UG-CNB) performed with specific uniform approach have never been evaluated in a large series of patients with lymphadenopathies suspected of lymphoma. The aim of this study was to assess the overall accuracy of UG-CNB in the lymph node histological diagnosis, using a standard reference based on pathologist consensus, molecular biology, and/or surgery. We retrospectively checked the findings concerning the application of lymph node UG-CNB from four Italian clinical units that routinely utilized 16-gauge diameter modified Menghini needle under power-Doppler ultrasonographic guidance. A data schedule was sent to all centers to investigate the information regarding techniques, results, and complications of lymph node UG-CNB in untreated patients over a 12-year period. Overall, 1000 (superficial target, n = 750; deep-seated target, n = 250) biopsies have been evaluated in 1000 patients; other 48 biopsies (4.5%), screened in the same period, were excluded because inadequate for a confident histological diagnosis. Most patients were suffering from lymphomas (aggressive B-cell non-Hodgkin lymphoma [aBc-NHL], 309 cases; indolent B-cell [iBc]-NHL, 279 cases; Hodgkin lymphoma [HL], 212 cases; and nodal peripheral T-cell [NPTC]-NHL, 30 cases) and 100 cases from metastatic carcinoma; 70 patients had non-malignant disorders. The majority of CNB results met at least one criterion of the composite reference standard. The overall accuracy of the micro-histological sampling was 97% (95% confidence interval: 95%-98%) for the series. The sensitivity of UG-CNB for the detection of aBc-NHL was 100%, for iBc-NHL 95%, for HL 93%, and for NPTC-NHL 90%, with an overall false negative rate of 3.3%. The complication rate was low (6% for all complications); no patient suffered from biopsy-related complications of grade >2 according to the Common Terminology Criteria for Adverse Events. Lymph node UG-CNB as mini-invasive diagnostic procedure is effective with minimal risk for the patient.

Pak1 pathway hyper-activation mediates resistance to endocrine therapy and CDK4/6 inhibitors in ER+ breast cancer.

Cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) have been approved in combination with endocrine therapy (ET) to treat estrogen receptor-positive (ER+) metastatic breast cancer (BC). However, drug resistance represents the leading cause of breast cancer patients mortality. This study aimed to identify novel resistance mechanisms to ER antagonists in combination with CDK4/6 inhibitors. We generated two ER+ BC cell lines, T47D and MCF7, resistant to the combination of the ER antagonist fulvestrant and CDK4/6i abemaciclib, named T47D-FAR and MCF7-FAR. Transcriptomic analysis revealed common up-regulation of genes involved in MAPK and epithelial to mesenchymal transition (EMT) pathways in FAR cells, sustaining their hyper-invasive phenotype and increased anchorage-independent growth, compared to sensitive cells. FAR cells showed higher p21-activated kinase 1 (Pak1) expression and phosphorylation levels than parental cells. PAK1 knockdown by siRNAs hampered cell proliferation, reduced anchorage-independent growth and invasive properties of T47D-FAR and MCF7-FAR, re-sensitizing them to fulvestrant and abemaciclib. Conversely, over-expression of PAK1 in MCF7 and T47D cells increased tumor spheroids' growth and invasion and reduced sensitivity to fulvestrant and abemaciclib, confirming its role in inducing drug resistance. Finally, treatment with Pak1 inhibitors, PF-3758309 (PF309) and NVS-PAK1-1, restored cell sensitivity to fulvestrant and abemaciclib of MCF7-FAR and T47D-FAR cells, both in vitro and in vivo. In conclusion, our data suggested a pivotal role for Pak1 in resistance to ET and CDK4/6i in ER+ breast cancers. These data might promote the rationale for the development of novel Pak1 inhibitors for treatment of patients with ER+ BC progressing on ET plus CDK4/6i.

Lamivudine 24-month-long prophylaxis is a safe and efficient choice for the prevention of hepatitis B virus reactivation in HBsAg-negative/HBcAb-positive patients with advanced DLBCL undergoing upfront R-CHOP-21.

Introduction: Occult hepatitis B infection (OBI) is a condition where replication-competent hepatitis B virus-DNA (HBV-DNA) is present in the liver, with or without HBV-DNA in the blood [<200 international units (IU)/ml or absent] in HB surface antigen (HBsAg)-negative/HB core antibody (HBcAb)-positive individuals. In patients with advanced stage diffuse large B-cell lymphoma (DLBCL) undergoing 6 cycles of R-CHOP-21+2 additional R, OBI reactivation is a frequent and severe complication. There is no consensus among recent guidelines on whether a pre-emptive approach or primary antiviral prophylaxis is the best solution in this setting of patients. In addition, questions still unresolved are the type of prophylactic drug against HBV and adequate prophylaxis duration. Methods: In this case-cohort study, we compared a prospective series of 31 HBsAg-/HBcAb+ patients with newly diagnosed high-risk DLBCL receiving lamivudine (LAM) prophylaxis 1 week before R-CHOP-21+2R until 18 months after (24-month LAM series) versus 96 HBsAg-/HBcAb+ patients (from January 2005 to December 2011) undergoing a pre-emptive approach (pre-emptive cohort) and versus 60 HBsAg-/HBcAb+ patients, from January 2012 to December 2017, receiving LAM prophylaxis [1 week before immunochemotherapy (ICHT) start until 6 months after] (12-month LAM cohort). Efficacy analysis focused primarily on ICHT disruption and secondarily on OBI reactivation and/or acute hepatitis. Results: In the 24-month LAM series and in the 12-month LAM cohort, there were no episodes of ICHT disruption versus 7% in the pre-emptive cohort (P = 0.05). OBI reactivation did not occur in any of the 31 patients in the 24-month LAM series versus 7 out of 60 patients (10%) in the 12-month LAM cohort or 12 out of 96 (12%) patients in the pre-emptive cohort (P = 0.04, by χ 2 test). No patients in the 24-month LAM series developed acute hepatitis compared with three in the 12-month LAM cohort and six in the pre-emptive cohort. Discussion: This is the first study collecting data regarding a consistent and homogeneous large sample of 187 HBsAg-/HBcAb+ patients undergoing standard R-CHOP-21 for aggressive lymphoma. In our study, 24-month-long prophylaxis with LAM appears to be the most effective approach with a null risk of OBI reactivation, hepatitis flare-up, and ICHT disruption.

Multiple predictive biomarker testing in melanoma: Another challenge in identifying the optimal approach on cytological samples.

BACKGROUND: The management of cutaneous melanoma has changed dramatically in recent years thanks to the development of tyrosine kinase and immune-checkpoint inhibitors (ICIs). Thus, multiple biomarker testing is becoming ever more important for the identification of patients who are potentially eligible for these treatments. One reliable approach to the molecular evaluation of metastatic melanoma is fine needle cytology (FNC). To examine the utility of this approach for assessing PD-L1 expression levels, we evaluated the cellular adequacy of residual cell block (CB) material from metastatic melanomas that were previously tested for BRAF and NRAS mutations. METHODS: We retrieved from our internal archives a series of FNC samples of metastatic melanoma that had been subjected to molecular testing on residual CB material or a dedicated needle rinse between January 2016 and July 2022. Real-time polymerase chain reaction was used to assess BRAF and NRAS status, and an SP263 assay was employed to ascertain PD-L1 expression levels. RESULTS: Overall, n = 19 cases were selected. Of these, 11 (57.9%) cases revealed a BRAF exon 15 p.V600E mutation, one case (5.3%) revealed NRAS mutation, and seven cases (36.8%) showed no mutations. Regarding PD-L1 assessment, 16/19 (84.2%) cases were deemed adequate, meaning they contained at least 100 viable cells. CONCLUSIONS: We highlighted the feasibility of assessing PD-L1 expression levels in residual CB material from metastatic melanomas previously tested for BRAF and NRAS mutations. Moreover, we pointed out that FNC needle rinses may be an alternative source of nucleic acids for molecular testing, preserving CB material for immunocytochemistry evaluation.

Reference standards for gene fusion molecular assays on cytological samples: an international validation study.

AIMS: Gene fusions assays are key for personalised treatments of advanced human cancers. Their implementation on cytological material requires a preliminary validation that may make use of cell line slides mimicking cytological samples. In this international multi-institutional study, gene fusion reference standards were developed and validated. METHODS: Cell lines harbouring EML4(13)-ALK(20) and SLC34A2(4)-ROS1(32) gene fusions were adopted to prepare reference standards. Eight laboratories (five adopting amplicon-based and three hybridisation-based platforms) received, at different dilution points two sets of slides (slide A 50.0%, slide B 25.0%, slide C 12.5% and slide D wild type) stained by Papanicolaou (Pap) and May Grunwald Giemsa (MGG). Analysis was carried out on a total of 64 slides. RESULTS: Four (50.0%) out of eight laboratories reported results on all slides and dilution points. While 12 (37.5%) out of 32 MGG slides were inadequate, 27 (84.4%) out of 32 Pap slides produced libraries adequate for variant calling. The laboratories using hybridisation-based platforms showed the highest rate of inadequate results (13/24 slides, 54.2%). Conversely, only 10.0% (4/40 slides) of inadequate results were reported by laboratories adopting amplicon-based platforms. CONCLUSIONS: Reference standards in cytological format yield better results when Pap staining and processed by amplicon-based assays. Further investigation is required to optimise these standards for MGG stained cells and for hybridisation-based approaches.

Relevance of the College of American Pathologists guideline for validating whole slide imaging for diagnostic purposes to cytopathology.

Whole slide imaging (WSI) allows pathologists to view virtual versions of slides on computer monitors. With increasing adoption of digital pathology, laboratories have begun to validate their WSI systems for diagnostic purposes according to reference guidelines. Among these the College of American Pathologists (CAP) guideline includes three strong recommendations (SRs) and nine good practice statements (GPSs). To date, the application of WSI to cytopathology has been beyond the scope of the CAP guideline due to limited evidence. Herein we systematically reviewed the published literature on WSI validation studies in cytology. A systematic search was carried out in PubMed-MEDLINE and Embase databases up to November 2021 to identify all publications regarding validation of WSI in cytology. Each article was reviewed to determine if SRs and/or GPSs recommended by the CAP guideline were adequately satisfied. Of 3963 retrieved articles, 25 were included. Only 4/25 studies (16%) satisfied all three SRs, with only one publication (1/25, 4%) fulfilling all three SRs and nine GPSs. Lack of a suitable validation dataset was the main missing SR (16/25, 64%) and less than a third of the studies reported intra-observer variability data (7/25, 28%). Whilst the CAP guideline for WSI validation in clinical practice helped the widespread adoption of digital pathology, more evidence is required to routinely employ WSI for diagnostic purposes in cytopathology practice. More dedicated validation studies satisfying all SRs and/or GPSs recommended by the CAP are needed to help expedite the use of WSI for primary diagnosis in cytopathology.

MMR profile and microsatellite instability status in colorectal mucinous adenocarcinoma with synchronous metastasis: a new clue for the clinical practice.

AIMS: Mucinous adenocarcinoma (MA) is associated with a high frequency of microsatellite instability (MSI). In the metastatic setting, it is crucial to establish mismatch repair (MMR) and/or MSI status. However, genetic heterogeneity between primary tumour and synchronous metastasis and the diagnostic accuracy of the assay may hamper the MMR/MSI status evaluation. METHODS: In this study, we assessed the concordance rate of the MMR/MSI status between primary tumour and paired synchronous metastasis of 25 MAs. MMR status was evaluated by immunohistochemistry (IHC), while MSI status was evaluated by using three different molecular approaches: microfluidic electrophoresis of PCR products (TapeStation 4200 platform), full-closed RTqPCR system (Idylla system) and multiplex amplification with fluorescent primers and subsequent DNA fragment analysis on an automated sequencer (Titano MSI test). RESULTS: The concordance rate between primary MA and metastasis was 21/21 (100%), 23/25 (92.0%), 23/25 (92.0%) and 21/25 (84%) by using IHC, Idylla system, Titano MSI test and TapeStation 4200 system. All the four methods used in our study displayed high concordant rate, ranging from 91.0% (IHC vs Tapestation 4200 platform) to 98.0% (IHC vs Titano). CONCLUSIONS: Several methodologies are frequently adopted in routine practice to successfully perform MMR/MSI status analysis. The most relevant issues related to MMR/MSI status analysis in MAs concern with low percentage of neoplastic cell and abundant mucine that may affect the molecular analysis. Thus, it might be useful to acquire both primary and metastatic sample to evaluate the MMR/MSI status by integrating IHC evaluation and molecular methodologies to successfully perform molecular profiling for MA patients.

Microsatellite instability evaluation of patients with solid tumour: routine practice insight from a large series of Italian referral centre.

DNA mismatch repair complex is involved in the maintenance of DNA stability. In the recent years, a plethora of technical approaches for microsatellite instability (MSI) analysis emerged. Here, we review the results of our MSI status evaluation by adopting a customised workflow on microfluidic system obtained in 4 years of diagnostic routine practice. Data from MSI status were retrieved from our institutional archive covering the period from January 2017 to December 2021. Microfluidic analysis was carried out on microfluidic platform. Results were inspected with a proprietary software. Overall, microsatellite stability (MSS) and MSI-high (MSI-H) profile was detected in n=423/458 (92.36%) and n=35/458 (7.64%) patients with metastatic CRC (mCRC), respectively. In addition, n=78/86 (90.70%) and n=8/86 (9.30%) patients without CRC showed an MSS and MSI-H profile. This review highlights the suitability of microfluidic approach in patients with cancer for MSI testing.

Evaluation of the Molecular Landscape in PD-L1 Positive Metastatic NSCLC: Data from Campania, Italy.

BACKGROUND: Immune-checkpoint inhibitors (ICIs) have increased and improved the treatment options for patients with non-oncogene-addicted advanced stage non-small cell lung cancer (NSCLC). However, the role of ICIs in oncogene-addicted advanced stage NSCLC patients is still debated. In this study, in an attempt to fill in the informational gap on the effect of ICIs on other driver mutations, we set out to provide a molecular landscape of clinically relevant oncogenic drivers in programmed death-ligand 1 (PD-L1) positive NSCLC patients. METHODS: We retrospectively reviewed data on 167 advanced stage NSCLC PD-L1 positive patients (≥1%) who were referred to our clinic for molecular evaluation of five driver oncogenes, namely, EGFR, KRAS, BRAF, ALK and ROS1. RESULTS: Interestingly, n = 93 (55.7%) patients showed at least one genomic alteration within the tested genes. Furthermore, analyzing a subset of patients with PD-L1 tumor proportion score (TPS) ≥ 50% and concomitant gene alterations (n = 8), we found that n = 3 (37.5%) of these patients feature clinical benefit with ICIs administration, despite the presence of a concomitant KRAS gene alteration. CONCLUSIONS: In this study, we provide a molecular landscape of clinically relevant biomarkers in NSCLC PD-L1 positive patients, along with data evidencing the clinical benefit of ICIs in patient NSCLC PD-L1 positive alterations.

A roadmap for a comprehensive diagnostic approach to fine needle cytology of lymph node metastases.

OBJECTIVE: Fine needle cytology (FNC) is widely used as a first-line procedure in the diagnostic algorithm of lymphadenopathies. In a metastatic setting, a first-line diagnostic approach identifies non-haematopoietic malignancy; however, cytopathologists could also provide a second diagnostic level, identifying the origin of the primary tumour. This paper outlines a comprehensive and practical approach to the cytological diagnosis of lymph node metastases. METHODS: Cytological diagnoses of lymph node metastases performed over a 10-year period were selected and divided into two groups. The first group, labelled "oncological," comprised patients with a previous history of malignancy; the second group, labelled "naïve," included patients with no relevant history. Pathology records were retrieved to record microscopic findings, namely, background appearance, group architecture, and specific cell features; data from cell block (CB) preparations were also collected. RESULTS: Overall, 982 cases were selected: 497 cases (50.61%) in the naïve group, and 485 (49.39%) in the oncological group. Overall, a second diagnostic level was achieved in 834/982 cases (84.92%); cases diagnosed as carcinoma not otherwise specified were more frequent in the naïve group than in the oncological group (17.51% vs. 8.04%, P < 0.01). Notably, although CB material was available in only 44.87% of the naïve cases, we were able to achieve a second diagnostic level thanks to the integration of clinical and cytomorphological findings, plus lymph node topography, in 82.49% of the cases. CONCLUSION: Our results confirmed that in a metastatic setting, FNC can reliably lead to the identification of the origin of the primary tumour.