Pancreaticobiliary tract cytology: Journey toward "Bethesda" style guidelines from the Papanicolaou Society of Cytopathology.

Abstract

The current series of articles related to the Papanicolaou Society of Cytopathology (PSC) guidelines for pancreaticobiliary cytology are the product of significant efforts by many experts working on different PSC guidelines committees.[1] The PSC guidelines for cytologic interpretation and reporting of variety of body site specimens have been described previously.[2,3,4,5,6] These are comparable to the guidelines from the National Cancer Institute for cervical cytology[7] and fine needle aspiration cytology of breast and thyroid.[8,9] Most of these systems are designed to stratify the risk of malignancy with diagnostic categories for guiding appropriate management algorithms. The current guidelines[10,11,12,13,14] follow the strategies comparable to the Bethesda System for Reporting Thyroid Cytopathology. The guidelines not only consider diagnostic categories and criteria, but also attempt to provide details on other aspects including techniques for obtaining specimens, which patient would benefit most from cytologic evaluation, information on ancillary testing, and patient follow-up/management. The scheme addresses the wide spectrum of approaches to acquire diagnostic material for cytopathologic evaluation from a variety of pancreaticobiliary lesions. A six-tiered system is recommended for the standardized nomenclature in pancreaticobiliary cytology. The categories proposed are: Non-diagnostic, negative, atypical, neoplastic (benign or other), suspicious, and positive.[12] “Atypical” and “suspicious” categories have relatively well reported malignancy risks.[15,16] Potentially, the most challenging and controversial category is “neoplastic (benign and other)” with the widest range of interpretations. The entities included in this category range from innocuous lesions such as benign cystic neoplasms (serous cystadenoma) to others like pre-malignant mucinous cysts (cystic mucinous neoplasm and intraductal papillary mucinous neoplasm), low-grade well-differentiated neuroendocrine tumors (NETs), and solid-pseudopapillary neoplasms. The premalignant mucinous cysts without unequivocal features of malignancy would fall in this category with very wide management options.[17] The NETs similarly have many challenges with controversies related to their categorical assignment. Due to their malignant potential, some favor these neoplasms be categorized as “malignant.” European Neuroendocrine Tumor Society (ENETS) and World Health Organization categorize low and intermediate grades of these as “tumor” or “neoplasm” in the absence of high-grade criteria (>50 mitoses per 50 high power field for NETs of pancreas and >20 mitoses per 10 high power field or Ki-67 index >20% for NETs of other sites).[18,19] Undoubtedly, the lesions with unequivocal cytological features of either small cell carcinoma or large cell undifferentiated carcinoma belong to the “malignant” category. An increasing trend with incidental NETs in surgically unfit older patients, favors a conservative approach for small NETs as an alternative management strategy. The categories proposed in the current guidelines permit practical flexibility by surgeons in order to assure that conservative strategies may be a better option than the surgery. This would be more confusing if these cases of low grade neoplasms automatically fell in a “malignant” category! Utilization of ancillary testing including molecular testing in cystic lesions is also addressed in appropriate areas.[13] With input from the guidelines by the National Cancer Center Network (www.nccn.org) and by the multidisciplinary international groups in the field of pancreatology, post cytologic evaluation and management are also covered.[14] A “triple test” approach similar to that applied for FNA of breast lesions is recommended. Patient management should be determined by correlating the clinical findings in concert with endoscopic, imaging, and cytologic findings. Effective application of such guidelines is heavily dependent on the collaborative, multidisciplinary interactions between endoscopists, pancreaticobiliary surgeons, radiologists, and cytopathologists. The current CytoJournal supplement issue with individual articles[10,11,12,13,14] covering various areas highlighted above would be a great resource under Open access platform[20,21] for all involved in the management of pancreaticobiliary lesions. These PSC guideline articles published under Open Access charter may be disseminated by multiple journals/platforms[22,23,24,25,26] including e-CytoJournal issue http://www.cytojournal.com/browse.asp?sabs=n.[27]