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

Abstract

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 Chiefly, the “neoplastic: benign” and “neoplastic: other” categories have been replaced by 2 new categories—“pancreatic neoplasia‐low‐grade” (PaN‐Low) and “pancreatic neoplasia‐high‐grade” (PaN‐High)—stratifying neoplastic mucinous cysts by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.

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

“…This standardized system has been reported to reduce nondiagnostic and atypical interpretations [12,24]. However, its implementation has received some criticism, especially for the controversial subcategory "neoplastic-other", which encompasses lesions of variable malignant potential (IPMNs and MCNs of all grades, also PanNETs and SPNs) [6].…”

“…The upcoming WHO international system aims to align cytology reporting with the recent WHO classification of the digestive system tumors, facilitating the communication among physicians of different specialties [6,7]. In this system, both "neoplastic-benign" and "neoplastic-other" PSC subcategories have been eliminated, whereas two new WHO categories-the "pancreatic neoplasm, low-risk/grade" and "pancreatic neoplasm, highrisk/grade"-have been established, encompassing IPMN or MCN with low-to intermediate and high-grade dysplasia, respectively.…”

“…In this system, both "neoplastic-benign" and "neoplastic-other" PSC subcategories have been eliminated, whereas two new WHO categories-the "pancreatic neoplasm, low-risk/grade" and "pancreatic neoplasm, highrisk/grade"-have been established, encompassing IPMN or MCN with low-to intermediate and high-grade dysplasia, respectively. In addition, SCA have been shifted from the "neoplastic-benign" PSC subcategory into the "benign/negative for malignancy" WHO category, while PanNETs and SPNs have been moved from the "neoplastic-other" PSC subcategory into the WHO category "positive for malignancy" (Figure 2) [6,7]. As the WHO cytology reporting system has not officially been published yet, evidence concerning its diagnostic value is still lacking.…”

“…Of interest, the World Health Organization (WHO) has been preparing an updated system for reporting pancreatobiliary cytopathology. Proposed changes include eliminating the "neoplastic: benign" PSC subcategory, while shifting SCA and lymphangioma interpretations into the "benign/negative for malignancy" WHO category; replacing the "neoplastic-other" PSC category with two new WHO categories, the "pancreatic neoplasm, low-risk/grade" and "pancreatic neoplasm, high-risk/grade", encompassing the interpretations of IPMN or MCN with low-to intermediate and high-grade dysplasia, respectively; and moving the PanNETs and SPNs from the "neoplastic-other" PSC subcategory into the WHO category "positive for malignancy", aligning with the recent WHO Classification of the Digestive System Tumors [6,7].…”

Evaluating Pancreatic and Biliary Neoplasms with Small Biopsy-Based Next Generation Sequencing (NGS): Doing More with Less

“…PanINs are microscopic lesions giving rise to most PDACs, whereas IPMNs and MCNs are macroscopic lesions [ 2 ]. Aside from PDAC, other examples of pancreatic malignancies include acinar cell carcinoma, solid pseudopapillary neoplasm (SPN), and the pancreatic neuroendocrine neoplasms (NENs), which comprise neuroendocrine tumors (NETs) and carcinomas (NECs) [ 9 , 10 ]. Whereas distinguishing a solid neoplasm (e.g., PDAC, another pancreatic malignancy or a metastasis) from pancreatitis is the main differential diagnosis in the evaluation of solid pancreatic lesions [ 11 , 12 ], cystic lesions encompass various pathologies including non-neoplastic (e.g., pseudocyst), neoplastic benign, such as serous cystadenoma (SCA), neoplastic mucinous carrying malignant potential (e.g., IPMN or MCN), and malignant entities (e.g., IPMN or MCN with associated invasive carcinoma) [ 12 , 13 , 14 , 15 ].…”