Endoscopic Ultrasound-Guided Fine Needle Aspiration Cytologic Evaluation of Intraductal Papillary Mucinous Neoplasm and Mucinous Cystic Neoplasms of Pancreas

Systematic review and meta-analysis of the Papanicolaou Society of Cytopathology (PSC) system in diagnosing pancreatic lesions: Evaluating diagnostic accuracy

INTRODUCTION

The Papanicolaou system plays a vital role in cytological evaluation, particularly in the diagnosis of pancreatic lesions. However, there is a lack of comprehensive evaluation regarding its diagnostic accuracy in pancreatic fine needle aspirations (FNAs). This study seeks to address this gap by conducting a systematic review and meta-analysis to assess the diagnostic accuracy of the Papanicolaou Society of Cytopathology (PSC) system in diagnosing pancreatic lesions.

METHODS

A systematic search of PubMed and EMBASE databases was conducted up to March 20, 2024, using predefined search terms related to pancreas, fine needle aspiration biopsy (FNAB), and diagnostic accuracy. The selected articles were assessed for risk of bias using the QUADAS-2 tool. A meta-analysis for sensitivity and specificity for each cut-off - namely, "Atypical considered positive", "Neoplastic considered positive", "Suspicious of Malignancy considered positive," and "Malignant considered positive" - was performed after excluding inadequate samples in each study. To assess diagnostic accuracy, summary receiver operating characteristic (sROC) curves were constructed, and the diagnostic odds ratio (DOR) was pooled.

RESULTS

Twelve studies met the inclusion criteria, comprising a total of 3604 cases. Sensitivity and specificity varied across the PSC categories, with the "Malignant" category showing the highest sensitivity (70%) and specificity (99%). The "Suspicious for malignancy and higher risk categories" demonstrated high sensitivity (81%) and specificity (97%).

CONCLUSION

This meta-analysis underscores the accuracy of the PSC system in reporting pancreatic aspirates. It highlights the significance of the "Suspicious" and "Malignant" categories in diagnosing malignancy, as well as the "Benign" and "Atypical" categories in ruling out malignancy.

The World Health Organization Reporting System for Pancreaticobiliary Cytopathology: Review and Comparison to the Papanicolaou Society of Cytopathology System

CONTEXT.—

The World Health Organization (WHO) Reporting System for Pancreaticobiliary Cytopathology (WHO System) is the product of a joint venture between the World Health Organization, the International Academy of Cytology, and the International Agency for Research on Cancer. The WHO System revises the Papanicolaou Society of Cytopathology System for Reporting Pancreaticobiliary Cytology (PSC System) and replaces the 6-tiered system with a 7-tiered system.

OBJECTIVE.—

To explain the WHO System and the differences with the PSC System.

DATA SOURCES.—

The WHO System and the PSC System of Reporting Pancreaticobiliary Cytopathology.

CONCLUSIONS.—

The diagnostic categories of the WHO System are "Insufficient/Inadequate/Nondiagnostic"; "Benign (Negative for Malignancy)"; "Atypical"; "Pancreaticobiliary Neoplasm, Low Risk/Low Grade (PaN-Low)"; "Pancreatic Neoplasm, High Risk/High Grade (PaN-High)"; "Suspicious for Malignancy"; and "Malignant." In the WHO System, the "benign" category includes both nonneoplastic and neoplastic lesions, so the "Neoplastic: Benign" category of the PSC system has been eliminated. Low-grade malignancies, pancreatic neuroendocrine tumors (PanNETs), and solid-pseudopapillary neoplasm (SPN) classified as "Neoplastic: Other" in the PSC System are classified as "Malignant" in the WHO System, leaving in the "Neoplasm" category intraductal lesions, which are divided into 2 new diagnostic categories: "Pancreaticobiliary Neoplasm (PaN)-Low Risk/Grade" and "PaN-High Risk/Grade." As with the PSC System, the WHO System advocates close correlation with imaging and encourages incorporation of ancillary testing into the final diagnosis, such as biochemical (carcinoembryonic antigen [CEA] and amylase) and molecular testing. The WHO System includes risk of malignancy per category, and reporting and diagnostic management options that recognize the variations in resources of low- and middle-income countries.

Reproducibility assessment of WHO reporting system for pancreaticobiliary cytopathology: A single institution experience

BACKGROUND

The World Health Organization (WHO) reporting system for pancreaticobiliary cytopathology was released to internationalize the reporting, assisting in correct diagnosis and patient treatment with significant revisions from the previous Papanicolaou Society of Cytopathology (PSC) system. The "neoplastic: benign" and "neoplastic: other" categories have mostly been superseded by two new ones: "pancreatic neoplasia-low-grade" (PaN-low) and "pancreatic neoplasia-high-grade" (PaN-high), which classify intermediate neoplastic lesions based on cytological atypia. We aim to assess the reproducibility and risk of malignancy (ROM) for reporting pancreaticobiliary cytopathology by the WHO system in comparison with the PSC system.

MATERIALS AND METHODS

A retrospective study by reviewing archival slides sent for pancreaticobiliary cytological evaluation from June 2021 to June 2023, by two pathologists blinded to each other's findings. Absolute ROM was determined by histopathology/cell block study/clinical follow-up (minimum 6 months)/overtly malignant imaging/metastasis.

RESULTS

A total of 332 cases from 329 patients met the inclusion criteria, comprising pancreatic, gallbladder, and biliary lesions. The median patient age was 54 years (range, 14-86 years). The overall sensitivity of the test is 74.9% specificity is 93.2%, positive predictive value of 96.8%, negative predictive value of 57.6%, and a diagnostic accuracy of 81.8%. The absolute ROM for each site in all categories was comparable with that of the published data from the WHO system.

CONCLUSION

Our study highlights the reliability of the WHO system for guiding clinical decision-making and patient management in the context of pancreaticobiliary. However, continual efforts among pathologists are essential to maintain consistent accuracy in cytological interpretations.

The World Health Organization classification of pancreaticobiliary cytopathology stratifies risk of malignancy and outcome for endoscopic ultrasound-guided fine-needle aspiration of the pancreas

BACKGROUND

The World Health Organization (WHO) has recently published a classification for reporting pancreaticobiliary cytopathology with differences compared to the Papanicolaou Society of Cytopathology (PSC) classification.

METHODS

Retrospective data were collected from pancreatic endoscopic ultrasound-guided fine-needle aspirations from 2014 to 2017 at a pancreatic cancer center. Absolute risk of malignancy (AROM), relative risk (to benign), performance characteristics, and overall survival were calculated for the entire cohort with comparison of cysts and solid lesions.

RESULTS

In total, 2562 cases were included: 16% cyst (n = 411) and 84% solid (n = 2151). The histologic confirmation rate was 43% (n = 1101) and the median follow-up (for benign) was 56 months. For WHO I-VII, overall AROM (%) was 23, 22, 62, 13, 65, 97, and 100; cyst AROM was 7, 0, 19, 13, 38, 78, and 100; and solid AROM was 50, 29, 70, 15, 100, 99, and 100. For PSC I-VI, overall AROM (%) was 23, 29, 64, 0 (IVa), 60 (IVb), 97, and 100; cyst AROM was 7, 0, 19, 0, 21, 78, and 100; and solid AROM was 50, 35, 73, 0, 92, 99, and 100. The difference in relative risk for a cyst (vs. solid) overall was 0.38 for WHO and 0.26 for PSC. WHO and PSC categories showed stratification for the probability of overall survival.

CONCLUSIONS

Cystic versus solid lesion type can dramatically affect AROM, particularly for nondiagnostic (I), benign (II), atypical (III), and WHO V categories. WHO IV conveys a similarly low AROM for cystic and solid types. Both classifications stratify the probability of overall survival, including the newly introduced categories WHO IV and WHO V.

Systematic review of challenging issues in pathology of intraductal papillary mucinous neoplasms

BACKGROUND

Intraductal papillary mucinous neoplasms (IPMNs) are a cystic precursor to pancreatic cancer. IPMNs deemed clinically to be at high-risk for malignant progression are frequently treated with surgical resection, and pathological examination of the pancreatectomy specimen is a key component of the clinical care of IPMN patients.

METHODS

Systematic literature reviews were conducted around eight topics of clinical relevance in the examination of pathological specimens in patients undergoing resection of IPMN.

RESULTS

This review provides updated perspectives on morphological subtyping of IPMNs, classification of intraductal oncocytic papillary neoplasms, nomenclature for high-grade dysplasia, assessment of T stage, distinction of carcinoma associated or concomitant with IPMN, role of molecular assessment of IPMN tissue, role of intraoperative assessment by frozen section, and preoperative evaluation of cyst fluid cytology.

CONCLUSIONS

This analysis provides the foundation for data-driven approaches to several challenging issues in the pathology of IPMNs.

It is not necessary to resect all mucinous cystic neoplasms of the pancreas: current guidelines do not reflect the actual risk of malignancy

BACKGROUND

Mucinous Cystic Neoplasms (MCN) of the pancreas are premalignant cysts for which current guidelines support pancreatic resection. The primary aim of this systematic review and meta-analysis is to define the pooled rate of malignancy for MCN.

METHODS

A systematic review of eligible studies published between 2000 and 2021 was performed on PubMed and Embase. Primary outcome was rate of malignancy. Data regarding high-risk features, including cyst size and mural nodules, were collected and analyzed.

RESULTS

A total of 40 studies and 3292 patients with resected MCN were included in the final analysis. The pooled rate of malignancy was 16.1% (95%CI 13.1-19.0). The rate of malignant MCN in studies published before 2012 was significantly higher than that of studies published after recent guidelines were published (21.0% vs 14.9%, p < 0.001). Malignant MCN were larger than benign (mean difference 25.9 mm 95%CI 14.50-37.43, p < 0.001) with a direct correlation between size and presence of malignant MCN (R2 = 0.28, p = 0.020). A SROC identified a threshold of 65 mm to be associated with the diagnosis of malignant MCN. Presence of mural nodules was associated with the diagnosis of a malignant MCN (OR = 4.34, 95%CI 3.00-6.29, p < 0.001).

CONCLUSION

Whereas guidelines recommend resection of all MCN, the rate of malignancy in resected MCN is 16%, implying that surveillance has a role in most cases, and that surgical selection criteria are warranted. Size and presence of mural nodules are significantly associated with an increased risk of malignant degeneration, small MCN and without mural nodules can be considered for surveillance.

Diagnostic Performance of Pancreatic Cytology with the Papanicolaou Society of Cytopathology System: A Systematic Review, before Shifting into the Upcoming WHO International System

The Papanicolaou Society of Cytopathology (PSC) reporting system classifies pancreatobiliary samples into six categories (I-VI), providing guidance for personalized management. As the World Health Organization (WHO) has been preparing an updated reporting system for pancreatobiliary cytopathology, this systematic review aimed to evaluate the risk of malignancy (ROM) of each PSC category, also the sensitivity and specificity of pancreatic FNA cytology using the current PSC system. Five databases were investigated with a predefined search algorithm. Inclusion and exclusion criteria were applied to select the eligible studies for subsequent data extraction. A study quality assessment was also performed. Eight studies were included in the qualitative analysis. The ROM of the PSC categories I, II, III, IV, V, VI were in the ranges of 8-50%, 0-40%, 28-100%, 0-31%, 82-100%, and 97-100%, respectively. Notably, the ROM IVB ("neoplastic-benign") subcategory showed a 0% ROM. Four of the included studies reported separately the ROMs for the IVO subcategory ("neoplastic-other"; its overall ROM ranged from 0 to 34%) with low (LGA) and high-grade atypia (HGA). ROM for LGA ranged from 4.3 to 19%, whereas ROM for HGA from 64 to 95.2%. When the subcategory IVO with HGA was considered as cytologically positive, together with the categories V and VI, there was a higher sensitivity of pancreatic cytology, at minimal expense of the specificity. Evidence suggests the proposed WHO international system changes-shifting the IVB entities into the "benign/negative for malignancy" category and establishing two new categories, the "pancreatic neoplasm, low-risk/grade" and "pancreatic neoplasm, high-risk/grade"-could stratify pancreatic neoplasms more effectively than the current PSC system.

Risk of malignancy associated with diagnostic categories of the proposed World Health Organization International System for Reporting Pancreaticobiliary Cytopathology

BACKGROUND

The World Health Organization (WHO) has proposed an updated international classification system for reporting pancreaticobiliary cytology. Substantial changes to the prior Papanicolaou Society of Cytopathology (PSC) system have been recommended. Chiefly, the "neoplastic: benign" and "neoplastic: other" categories have been replaced by 2 new categories-"pancreatic neoplasia-low-grade" (PaN-Low) and "pancreatic neoplasia-high-grade" (PaN-High)-stratifying neoplastic mucinous cysts by cytological atypia. Low-grade malignancies are placed in the "malignant" category and benign serous cystadenoma in the "benign/negative" category. Risk of malignancy (ROM) associated with the diagnostic categories of the WHO system has yet to be defined.

METHODS

All patients who underwent endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) for a pancreatic lesion at a single institution from January 2016 to December 2016, prospectively classified using the PSC system, were reclassified using the WHO system. Absolute ROM was determined by histologic outcome and/or clinical follow-up of at least 6 months.

RESULTS

A total of 334 EUS-FNA samples from 322 patients were reviewed and reclassified. Absolute ROM for the WHO system was 7.7% for "insufficient/inadequate/nondiagnostic" category, 1.0% for "benign/negative for malignancy," 28.0% for "atypical," 4.8% for "PaN-Low," 60.0% for "PaN-High," 100% for "suspicious for malignancy," and 100% for "malignant;" the absolute ROM for the same cohort using the PSC system was 7.7% for "nondiagnostic" category, 1.0% for "negative (for malignancy)," 28.0% for "atypical," 0.0% for "neoplastic: benign," 30.3% for "neoplastic: other," 100% for "suspicious (for malignancy)," and 100% for "positive or malignant."

CONCLUSIONS

The WHO international system achieves improved stratification by associated ROM compared to the PSC system.

Intraductal papillary mucinous neoplasm of the pancreas: Cytomorphology, imaging, molecular profile, and prognosis

BACKGROUND

Intraductal papillary mucinous neoplasm (IPMN) constitutes up to 20% of all pancreatic resections, and has been increasing in recent years. Histomorphological findings of IPMN are well established; however, there are not many published papers regarding the cytological findings of IPMN on fine needle aspiration (FNA) specimens. We review the cytomorphological features, molecular profile, imaging findings, and prognosis of IPMN.

METHODS

The English literature was thoroughly searched with key phrases containing IPMN.

OBSERVATIONS

IPMN is a rare entity, affecting men and women equally and is usually diagnosed at the age of 60-70 years. The characteristic imaging features include a cystic lesion with associated dilatation of the main or branch pancreatic duct, and atrophy of surrounding pancreatic parenchyma. Cytomorphological features of IPMN include papillary fragments of mucinous epithelium in a background of abundant thick extracellular mucin, a hallmark feature. IPMNs should be evaluated for high-grade dysplasia, which manifests with nuclear atypia, nuclear moulding, prominent nucleoli, nuclear irregularity, and cellular crowding. Molecular profiling of IPMN along with carcinoembryonic antigen and amylase levels is useful in predicting malignancy or high-grade dysplasia arising in IPMN. Overall, the prognosis of IPMN is excellent except in those cases with high-grade dysplasia and malignant transformation. Postoperative surveillance is required for resected IPMNs.

CONCLUSION

IPMN requires a multidisciplinary approach for management. Cytomorphological findings of IPMN on FNA, in conjunction with tumour markers in pancreatic fluid cytology and imaging findings, are of paramount importance in clinical decision-making for IPMN.