Categorisation of serous effusions using the International System for Reporting Serous Fluid Cytopathology and assessment of risk of malignancy with diagnostic accuracy

The International System for Reporting Serous Fluid Cytopathology: A Systematic Review and Meta-Analysis of Diagnostic Test Accuracy Studies

This is the first systematic review and meta-analysis of The International System (TIS) for reporting serous fluid cytopathology. Our aims were to present the pooled malignancy rate of each TIS reporting category and the diagnostic accuracy of cytology using this system. Database search using a predefined strategy was followed by study selection, data extraction, study quality assessment, and statistical analysis. Data derived from 16 eligible studies were pooled. The pooled rates of malignancy were as follows: 27% (95% CI; 16%-41%) for "nondiagnostic" (ND), 11% (95% CI; 7%-18%) for negative for malignancy" (NFM), 49% (95% CI; 37%-61%) for "atypia of undetermined significance" (AUS), 90% (95% CI; 81%-95%) for "suspicious for malignancy" (SFM), and 100% (95% CI; 98%-100%) for "positive for malignancy" (MAL). Studies performed exclusively in cancer hospitals showed higher pooled malignancy rates, compared with academic and community hospitals serving the general population, in the ND [40% (95% CI; 21%-62%) vs. 22% (95% CI; 11%-39%)], NFM [20% (95% CI; 13%-30%) vs. 9% (95% CI; 5%-17%)], and AUS categories [55% (95% CI; 47%-63%) vs. 46% (95% CI; 31%-62%)]. Notably, the difference was significant in the NFM category ( P =0.04). When both SFM and MAL cytology interpretations were considered as malignant outcomes, the pooled sensitivity and specificity were 68.74% (95% CI; 59.90%-76.39%) and 98.81% (95% CI; 98.18%-99.22%), respectively. In addition, the diagnostic odds ratio (DOR) was found to be 170.7 (95% CI; 96.2-303.3). Despite its strengths, our study also had some limitations. Therefore, future large-scale longitudinal studies could strengthen the findings of this review.

Application of the newly published International System for Reporting Serous Fluid Cytopathology in atypical and suspicious diagnosis: a four-year retrospective analysis

INTRODUCTION

Serous fluids offer crucial diagnostic insights, but inconsistent analysis hampers reporting quality, especially in indeterminate (ID) categories like atypia of undetermined significance (AUS) and suspicious for malignancy (SFM). The 2020 International System for reporting Serous Fluid Cytopathology (TIS) aims to standardize communication and reduce reporting disparities. This study evaluates TIS's role in AUS and SFM categories within our institution.

MATERIALS AND METHODS

A 4-year retrospective search of cytopathology reports from December 2015 to December 2019 for AUS and SFM diagnoses in pleural, ascitic, pericardial fluids, and peritoneal washings was performed and results reclassified using TIS definitions. The risk of malignancy (ROM) was calculated for existing and reclassified diagnoses.

RESULTS

Over 4 years, we received 2998 serous fluid specimens. AUS constituted 2.3% (70 cases), while SFM constituted 0.5% (16 cases). Excluding repeats, 80 cases were TIS-reviewed. Sixteen cases of ID diagnoses were reclassified. Two cases of AUS were changed to negative for malignancy (NFM) and 12 to SFM. Two SFM cases were upgraded to malignancy. ROM shifted from 63% to 60% for AUS and 100% to 85% for SF (TIS's ROM range: AUS: 66% ± 10%; SFM: 82% ± 4.8%).

CONCLUSIONS

This institution's ID diagnosis rate is low. AUS ROM is challenging but aligns with TIS, primarily favoring benign. All SFM diagnoses are highly suspicious but quantitatively inadequate for definitive malignancy, explaining the elevated ROM. AUS rate should gauge quality, not serve as a catch-all category. Algorithmic cytology with cell blocks and ancillary studies aids reclassification. TIS is user-friendly and is a consistent methodology for standardized reporting. Further studies are needed to evaluate ROM and define reproducible diagnostic criteria for each category for better system utilization.

Deciphering Serous Effusions Using the New International System for Reporting Serous Fluid Cytopathology

Introduction Serous effusion cytopathology is a minimally invasive, cost-effective procedure and plays a crucial role in diagnosing a spectrum of pathological conditions, ranging from benign to malignant. The International System for Reporting Serous Fluid Cytopathology (ISRSFC) offers a standardized framework for reporting serous effusions, aiding in better communication and clinical decision-making. Aims and objectives This study aimed to categorize effusions using the ISRSFC reporting system. In addition, we sought to estimate the risk of malignancy (ROM) for each diagnostic category and evaluate the diagnostic performance of conventional smear versus cell block techniques. Materials and methods This cross-sectional study was conducted in the Department of Pathology over one year. We applied the ISRSFC criteria to serous effusions and categorized them accordingly. The ROM for each category was assessed with histopathology serving as the gold standard. Then, the diagnostic performance including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy was evaluated using conventional smear and cell block techniques. Results The study included 185 serous effusion cases, with ages ranging from two months to 85 years. The male-to-female ratio was 1.1:1. Most effusions were pleural fluids constituting about 133 cases (71.9%), followed by peritoneal fluids (47 cases, 25.4%) and pericardial fluids (five cases, 2.7%). Among the fluids, four (2.2%) were diagnosed as non-diagnostic (ND), 152 (82.2%) as negative for malignancy (NFM), four (2.2%) as atypia of undetermined significance (AUS), nine (4.8%) as suspicious for malignancy (SFM), and 16 (8.6%) as malignant (MAL). The overall ROM was 25% for ND, 8.5% for NFM, 50% for AUS, 77% for SFM, and 100% for MAL. The sensitivity, negative predictive value (NPV), and diagnostic accuracy were superior when combining conventional smear with the cell block technique. Conclusions Our findings underscore the use of ISRSFC in categorizing effusion samples, assessing the ROM, and guiding clinical management. Moreover, our study highlights the benefits of employing a combined approach using conventional smears and cell blocks for enhanced diagnostic accuracy in serous effusions.

Diagnostic accuracy of International System for Reporting Serous Fluid Cytopathology: A systematic review and meta-analysis in malignancy diagnosis

This study conducts the first meta-analysis to assess the aggregated risk of malignancy associated with each category of the International System for Reporting Serous Fluid Cytopathology (ISRSFC) for reporting serous effusion cytology, while also evaluating diagnostic accuracy. PubMed/MEDLINE and Embase were systematically searched using the keywords "(pleural, peritoneal, and pericardial effusions) AND (serous effusion cytology) OR (International System for Reporting Serous Fluid Cytopathology)". Articles underwent risk of bias assessment using the QUADAS-2 tool. After excluding inadequate samples, a meta-analysis determined sensitivity and specificity for different cutoff points, including "atypical considered positive," "suspicious of malignancy considered positive," and "malignant considered positive." Summary receiver operating characteristic curves assessed diagnostic accuracy, and the diagnostic odds ratio was pooled. Sixteen retrospective cross-sectional studies, totaling 19,128 cases, were included. Sensitivity and specificity for the "atypical and higher risk categories" considered positive were 77% (95% confidence interval [CI], 68%-84%) and 95% (95% CI, 93%-97%) respectively. For the "suspicious for malignancy and higher risk categories" considered positive, sensitivity and specificity were 57% (95% CI, 49%-65%) and 100% (95% CI, 99%-100%) respectively. Sensitivity and specificity for the "malignant" category considered positive for malignancy were 70% (95% CI, 60%-77%) and 99% (95% CI, 98%-99%), respectively. The pooled area under the curve ranged from 85% to 89.5% for each cutoff. This meta-analysis underscores the ISRSFC's accuracy in reporting serous fluid cytology. It emphasizes the diagnostic importance of the "suspicious" and "malignant" categories in identifying malignancy, and the role of the "benign" category in ruling out malignancy.

Comprehensive evaluation of benign and malignant etiologies of different serous effusions with the International System for Reporting Serous Fluid Cytopathology: A multi-institutional study in Taiwan

BACKGROUND

The International System for Reporting Serous Fluid Cytopathology (ISRSFC) was introduced globally in 2019 in response to the absence of a standardized reporting system for serous fluid cytology. This study presents experiences implementing this system across three distinct hospitals in Taiwan.

METHODS

A total of 6177 serous fluid specimens in three hospitals in Taiwan between 2018 and 2020 were retrospectively reviewed and reclassified according to the ISRSFC. Cytohistological correlation and chart review were further performed to investigate etiologies and risks of malignancy (ROMs).

RESULTS

Reclassification showed that 34 (0.7%) of 4838 pleural effusions were nondiagnostic (ND), 4086 (84.5%) were negative for malignancy (NFM), 201 (4.2%) were atypia of undetermined significance (AUS), 92 (1.9%) were suspicious for malignancy (SFM), and 425 (8.8%) were malignant (MAL). The 1231 ascites cases contained 13 (1.1%) ND, 1004 (81.6%) NFM, 53 (4.3%) AUS, 31 (2.5%) SFM, and 130 (10.6%) MAL specimens. In pleural effusions, the ROM was 2.9% for ND, 14.0% for NFM, 52.2% for AUS, 85.9% for SFM, and 95.1% for MAL. In ascites, it was 15.4% for ND, 19.1% for NFM, 52.8% for AUS, 83.9% for SFM, and 92.3% for MAL. In pericardial effusions, it was 0.0% for ND, 11.6% for NFM, 30.8% for AUS, 100.0% for SFM, and 95.2% for MAL. Different effusions' most common benign and malignant etiologies were also disclosed.

CONCLUSIONS

These multi-institutional data have determined the diagnostic usefulness of the ISRSFC, which provides pathologists and physicians with invaluable assistance in correctly classifying effusions for further management.

Review of the impact of the International System for Serous Fluid Cytopathology

The International System for Reporting Serous Fluid Cytology (TIS) has been proposed by an expert working team composed of the International Academy of Cytology and the American Society of Cytopathology, following an international survey. Since its introduction, the TIS has gained worldwide acceptance, and this review aims to assess its global impact. A literature search revealed 25 studies which have presented data on the impact of the TIS. Most of them provide data, including risk of malignancy (ROM) for each diagnostic category, separately for pleural, peritoneal and pericardial effusions, while a few do not separate them. A few studies focus on specific diagnoses like mesothelioma on specific types of fluids or more specific issues like the optimal fluid volume for cytology or interobserver variability. A synopsis of the data from the literature search is presented in four tables. The ROM assessment is discussed, as well as interobserver variability and the use of ancillary diagnostic immunochemistry. In conclusion, our review of the published data suggests that the TIS is a valid classification scheme that has been widely accepted by pathologists globally, is highly reproducible and makes a valuable contribution to clinical therapeutic management.

Categorisation of peritoneal serous effusions using the International System for Reporting Serous Fluid Cytopathology-A study on gynaecological samples

BACKGROUND

Cytology of serous effusions is an indispensable diagnostic tool for the diagnosis of non-neoplastic as well as neoplastic effusions, aiding in the categorisation, staging, and prognostication of the patient. This study focuses on reclassifying cases of peritoneal fluid cytology following the International System for Reporting Serous Fluid Cytopathology (TIS), highlighting various challenges encountered and adding to the body of data regarding the risk of malignancy (ROM), focussing on peritoneal effusions due to gynaecological causes.

METHODS

Peritoneal effusion samples were retrieved from our department's archives and reclassified according to the TIS. The ROM for each category was calculated based on available surgical follow-up.

RESULTS

A total of 818 peritoneal effusions were studied. Following the definitions and guidelines of the TIS, the cases were reclassified with 125 (15.2%) in the category of non-diagnostic (ND), 595 (72.7%) as negative for malignancy (NFM), 26 (3.2%) as atypia of undetermined significance (AUS), 12 (1.5%) as suspicious for malignancy (SFM), and 60 (7.3%) as malignant (MAL). The respective ROM values for each category were 16.9%, 12.1%, 50%, 80%, and 100%, respectively. By considering the MAL and SFM groups as positive, and the ND, NFM, and AUS groups as negative, the diagnostic accuracy, sensitivity, specificity, and positive and negative predictive values were determined as 85.2%, 36.7%, 99.1%, 91.7%, and 84.5%, respectively.

CONCLUSIONS

Peritoneal cytology categorisation following the proposed TIS offered a practical approach for categorisation of the fluids received. The ROMs reported in our study were mostly concordant with those published according to the TIS.

Risk of malignancy assessment of the International System for Reporting Serous Fluid Cytopathology: Experience in a community hospital setting and comparison with other studies

BACKGROUND

The International System for Reporting Serous Fluid Cytopathology (ISRSFC) was published recently to provide standard reporting terminology for serous fluid. To date, several ISRSFC reclassification studies have reported a wide range of diagnostic category frequency and the associated risk of malignancy (ROM). Herein, the authors applied the ISRSFC to report pleural and peritoneal effusions retrospectively in a community hospital setting.

METHODS

With Internal Review Board approval, 446 peritoneal effusion specimens and 299 pleural fluid specimens from 576 patients in three community hospitals over a 12-month period were reviewed and reclassified according to the ISRSFC.

RESULTS

After reclassification, in pleural effusions, 18 (5.0%) were nondiagnostic (ND), 273 (76.0%) were negative for malignancy (NFM), 18 (5.0%) were atypia of undetermined significance (AUS), 6 (1.7%) were suspicious for malignancy (SFM), and 44 (12.3%) were malignant (MAL). In peritoneal effusions, after reclassification, 11 (5.5%) were ND, 168 (77.1%) were NFM, 9 (4.1%) were AUS, 2 (0.9%) were SFM, and 27 (12.4%) were MAL. The calculated ROM was 0.0% for ND, 1.8% for NFM, 37.5% for AUS, 83.3% for SFM, and 100.0% for MAL in peritoneal effusions; and the ROM was 8.3% for ND, 1.2% for NFM, 44.4% for AUS, and 100.0% for both SFM and MAL in pleural effusions. Further analysis demonstrated notable heterogeneity among published ISRSFC reclassification studies, although the overall ROMs did not differ significantly from the ISRSFC-determined ROMs (all p values were > .05 for mean ROM comparisons).

CONCLUSIONS

The findings suggested the necessity for each laboratory to perform its own ROM analysis based on its statistics for ISRSFC-tiered classification terminology.

Cytomorphological and immunohistochemical features of pancreatic ductal adenocarcinoma in serous fluids

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) represents the most common primary pancreatic malignancy. An understanding of the cytomorphologic features of conventional ductal adenocarcinoma and its variants is important to ensure accurate diagnoses.

METHODS

The clinicopathological and cytological data of serous fluids in PDAC patients were obtained from the electronic medical records and pathology database. All samples were analyzed and reclassified according to the "The International System for Reporting Serous Fluid Cytopathology" guidelines. Cytomorphologic features were examined with SurePath automatically prepared slides and stained using the Pap method in malignant (MAL) effusion specimens from 21 patients with PDAC. Immunocytochemical staining was conducted on 12 cell blocks from MAL PDAC effusion.

RESULTS

A total of 137 serous fluids specimens of PDACs were included, among which 61 (44.5%), 9 (6.6%), 13 (9.5%), 52 (38.0%), and 2 (1.5%) patients were classified into malignancy, suspicious for malignancy, atypia of undetermined significance, negative for malignancy and nondiagnostic groups, respectively. The key cytologic features for the conventional type of PDAC included cohesive clusters of ductal cells in glandular crowding and disorganized "drunken honeycomb" pattern or intercalated duct-like structure with anisonucleosis, cytoplasmic vacuoles, and concomitant "Indian-file" configuration. Undifferentiated carcinoma was comprised of enlarged, undifferentiated, pleomorphic MAL cells. Adenosquamous carcinoma could show glandular and/or squamous differentiation. Colloid carcinoma was composed of three-dimensional cancer cell clusters floating in thick mucin.

CONCLUSION

Crowding and disorganized "drunken honeycomb" pattern or intercalated duct-like structure with anisonucleosis, may represent an important clue for diagnosing PDAC in serous fluids. Immunocytochemical staining in combination with review of medical records and cytomorphological data can serve as useful adjuncts for distinguishing between PDAC and its variants.