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.

Role of Ancillary Techniques in Reporting Serous Fluid Cytology - "Redefining Categories, Refining Diagnosis"

Background

The "International System of Reporting Serous Fluid Cytology (TIS)" together with cytomorphology promotes the use of ancillary techniques to resolve difficulties in reporting serous fluid cytology.

Objective

To classify serous effusion fluid samples received at our department in line with "TIS", indicating the risk of malignancy (ROM), and directing appropriate usage of ancillary testing.

Materials and Methods

Prospective study carried out from October 2021 to September 2022. The study included all pleural, ascitic, and pericardial fluid samples, reported according to 'TIS'. Flow cytometry and immunocytochemistry were ancillary methods utilized to assist in reporting. Cases with available history and convincing correlations didn't require further assessment.

Results

A total of 1200 serous effusion samples were evaluated including 604 pleural, 591 ascitic, and 5 pericardial fluid samples. After categorization, there were 23 samples in non-diagnostic (ND, 1.9%), 575 in negative for malignancy (NFM, 47.91%), 44 in atypia of undetermined significance (AUS, 3.66%), 64 in suspicious for malignancy (SFM, 5.33%), and 494 in malignant category (MAL, 41.16%). Ancillary studies were beneficial in the recategorization of 26% (11/44) AUS cases, 29.6% (19/64) SFM cases, and it helped refine tumor characteristics in 35.42% (175/494) cases categorized as malignant. Final ROM calculated for each category: ND 25%, NFM 18.6%, AUS 66.6%, SFM 88%, and MAL 100%.

Conclusion

Serous fluid is an easily obtainable sample that can provide opportunities for ancillary testing with clinical implications. In AUS and suspicious category although, diagnostic yield is increased however, a larger number of cases are required to obtain definite results.

Application of algorithmic cytomorphological assessment and immunocytochemistry with the international system for reporting serous fluid cytopathology on pericardial fluid cytology

AIMS

The international system for reporting serous fluid cytopathology (ISRSFC) set forth a five-tiered reporting system with comprehensive validation on pleural and peritoneal fluid cytology. An algorithmic approach for cytomorphological assessment and immunocytochemistry was also described in ISRSFC. Limited data on pericardial fluid are supportive but would benefit from further investigation.

METHODS

Consecutive pericardial fluid cytology over a 4-year period was reviewed by multiple board-certified pathologists according to the ISRSFC. Cytomorphology and immunocytochemistry were assessed sequentially, with respective diagnostic performances computed and compared. Literature review was performed.

RESULTS

In total 358 specimens, including 53 with immunocytochemistry available, were reviewed. There were 137 benign and 221 malignant (MAL) cases. The risks of malignancy were 23.5% non-diagnostic (ND), 29.2% negative for malignancy (NFM), 56.0% atypia of undetermined significance (AUS), 82.6% suspicious for malignancy (SFM) and 99.2% (MAL) for cytomorphological assessment, improving to 23.5% (ND), 29.1% (NFM), 56.8% (AUS), 78.9% (SFM) and 99.3% (MAL) incorporating immunocytochemistry. Ten cases (2.8%) received a change in diagnosis after review of immunocytochemistry. All revisions of diagnostic category were appropriate upgrades/downgrades referenced against clinical information. Cytomorphological typing was accurate for adenocarcinoma (n=81/83, 97.6%), while other carcinomas and lymphomas required immunocytochemistry. Certain subcategories within AUS and SFM pertaining to bland indeterminate epithelial cells or mucinous material were not seen for pericardial fluid.

CONCLUSIONS

The ISRSFC shows robust diagnostic performance for pericardial fluid cytology. For pericardial effusion, disease composition and applicable cytological subcategories differ from its peritoneal and pleural counterparts. Incorporating immunocytochemistry by an algorithmic approach improves diagnostic accuracy. Cytomorphology is accurate for identifying adenocarcinomas, but further typing necessitates immunocytochemistry is necessary.

Application of the International System for Reporting Serous Fluid Cytopathology with Cytohistological Correlation and Risk of Malignancy Assessment

The International System for Reporting Serous Fluid Cytopathology (TIS) classifies serous effusions into five categories: non-diagnostic (ND), negative for malignancy (NFM), atypia of unknown significance (AUS), suspicious for malignancy (SFM) and malignant (MAL). The main objectives of this classification comprise the establishment of a universal code of communication between cytopathologists and clinicians and histopathologists, as well as between different laboratories worldwide, paving the way for the setting of clinical management guidelines based on the risk of malignancy assessment for each diagnostic category. We retrieved the total number of pleural and peritoneal effusion cases of our department for the three-year time period between 2018 and 2020, yielding a total of 528 and 500 cases, respectively. We then proceeded to reclassify each specimen according to TIS guidelines and calculate the risk of malignancy (ROM) for each category by searching each patients’ histology records, medical history and clinical follow-up. For pleural effusions, 3 (0.57%) cases were classified as ND, 430 (81.44%) cases as NFM, 15 (2.84%) as AUS, 15 (2.84%) as SFM and 65 (12.31%) as MAL. ROM amounted to 0%, 5.3%, 33.33%, 93.33% and 100% for each category, respectively. As far as peritoneal effusions are concerned, 6 (1.2%) were categorized as ND with ROM estimated at 16.66%, 347 (69.4%) as NFM (ROM = 9%), 13 (2.6%) as AUS (ROM = 38.46%), 12 (2.4%) as SFM (ROM = 83.33%) and 122 (24.4%) as MAL (ROM = 100%). Our results underline the utility of the current classification, both as a means of communication between doctors of different specialties and as general guidelines for the further clinical management of patients.

Cytologic diagnosis of "atypical" in serous fluid cytopathology. Approach of the international system for reporting serous fluid cytopathology

Diagnostic uncertainty may occur with almost any entity on cytological evaluation, depending on the quality and quantity of the provided sample. In serous fluid cytopathology, until recently, there had been no defined or agreed criteria for atypia and suspicious categories. Historically, the two descriptive terms appear to have been used almost interchangeably. The international system for serous fluid cytopathology is the first attempt by an expert international authorship to suggest the scenarios in which these terms are used and propose some diagnostic criteria and clinical management strategies.

Cytohistological Correlation in Pleural Effusions Based on the International System for Reporting Serous Fluid Cytopathology

The International System for Reporting Serous Fluid Cytology (TIS) was recently developed. Given its novelty, most studies looking into the risk of malignancy (ROM) of serous effusion diagnostic categories were published before the development of TIS. We searched the database of our department for pleural effusions diagnosed in the last five years, excluding those without a corresponding pleural biopsy. Cases were reviewed and reclassified according to the TIS. A cytohistological correlation was performed. In total, 350 pleural effusion specimens with one or more corresponding pleural biopsies were included. After reclassification, 5 (1.43%) were nondiagnostic (ND), 253 (72.29%) were negative for malignancy (NFM), 7 (2.00%) had atypia of unknown significance (AUS), 14 (4.00%) were suspicious for malignancy (SFM), and 71 (20.57%) were malignant (MAL). Calculated ROM was 40% for ND, 20.16% for NFM, 42.86% for AUS, 78.57% for SFM, and 100% for MAL. Effusion cytology sensitivity and specificity were 60.29% and 98.56%, respectively. This is the first publication looking into the cytohistological correlation of a retrospective cohort of pleural effusions based on the TIS. We add to the body of data regarding the ROM for TIS categories, highlighting areas of potential future research.