LAUSR

In 2014, the Papanicolaou Society of Cytopathology (PSC) published its guidelines for reporting pancreatobiliary cytopathology codified in an atlas in 2015. As with terminology reporting systems for other organs, this system included 6 diagnostic categories with definitions for each. The definitions for the “atypical” category, “suspicious,” and “positive/malignant” were like the definitions in other systems. Unique to the PSC system is that it defined adequacy for pancreatobiliary specimens, especially pancreatic cysts, and it created categories of “neoplasm: benign” and “neoplasm: other.” Serous cystadenomas (SCA) were classified as “neoplasm: benign and neoplastic mucinous cysts,” which include intraductal papillary neoplasms and mucinous cystic neoplasms as neoplasm: other. A controversial aspect of the PSC system was the inclusion of “pancreatic neuroendocrine neoplasm” (PanNET) and “solid pseudopapillary neoplasm” (SPN) in the neoplasm: other category. This was done to allow for more flexible patient management because PanNET may occasionally be managed with observation. The proposed World Health Organization (WHO) International System to update the PSC system follows the WHO Classification of Tumours of the Pancreas published in 2019. SCA are now classified as “benign/negative for malignancy,” and PanNET and SPN are in the “malignant” category. Two new categories have been created: “pancreatobiliary neoplasmlowrisk/grade” (PaNLow) and “pancreatobiliary neoplasmhighrisk/grade” (PaNHigh). These categories stratify intraductal and cystic mucinous neoplasms by cytological grade using previously published criteria. In this months’ issue, Hoda et al report on the risk of malignancy (ROM) for each diagnostic category using the WHO International System for Pancreatobiliary Cytology in a previously studied cohort of patients classified prospectively using the PSC system. The study includes 334 endoscopic ultrasoundguided fineneedle aspiration samples derived from 322 patients and retrospectively classifies the samples into the diagnostic categories of the proposed WHO International System. The absolute ROM is established by correlation with histology or clinical followup. Notably, highgrade dysplasia in an intraductal or intracystic process is defined as malignant. The restructuring of the neoplasm category led to improved prediction of ROM. Under the PSC system, the neoplasm: benign category had a 0% ROM and the neoplasm: other category had a 30% ROM. Using the WHO International System, 4 cases previously classified as neoplasm: benign were reclassified as benign/negative for malignancy. Sixtysix cases classified as neoplasm: other were reclassified as PaNLow (42), PaNHigh (5), and malignant (19). The PaNLow category has a 5% ROM and the PaNHigh category has a 60% ROM. The ROM in the other categories remained the same. Two cases in the PaNLow category, confirmed as mucinous