Diagnostic Accuracy of Endoscopic Ultrasound-Guided Fine Needle Aspiration Cytology of Pancreatic Lesions

Pancreatic cancer is notorious for its poor prognosis, with a low overall 5-year survival rate of merely 8.7%. It is the fifth leading cause of cancer-related mortality in South Korea [1] because of the delayed detection of tumors, typical presentation at an advanced stage, and its aggressive disease behavior. Only 20% of tumors are surgically resectable when detected. Remaining 80% of patients cannot help undergoing palliative therapy, the only treatment practical for those with unresectable tumor. In addition, pancreatic cancer has a poor response to chemotherapy and radiation therapy, increasing the complexity of patient management. Therefore, early detection is key in order to increase the survival rate of pancreatic cancer patients and to improve overall patient care. Early detection, though it is crucial, is challenging since pancreatic cancer is usually asymptomatic in the initial stage and anatomically less accessible due to surrounding organs in the retroperitoneum. To overcome these limitations, imaging modalities such as abdominal ultrasound, computed tomography, magnetic resonance imaging, endoscopic retrograde cholangiopancreatography, endoscopic ultrasonography (EUS), and positron emission tomography have been used to localize the lesions. For the detection of pancreato-biliary diseases, EUS is currently widely accepted. This technique enables precise visualization of the lesion and the ability to proficiently determine the depth of gastrointestinal malignancies [2]. By combining the advantages of EUS with fine-needle aspiration cytology (FNAC) for the retrieval of specimens for pathologic diagnosis, EUS-FNAC has improved diagnostic capabilities. With EUS-FNAC, distinguishing pancreatic cancer from chronic pancreatitis, detection of tumor smaller than 2 cm and staging of the cancer are superior to those with the other modalities. EUS-FNAC has become the most popular technique with which to obtain cytology specimens and diagnose patients suspected to have pancreatic malignancy. EUS-FNAC has been shown to be diagnostically useful, obviating unwarranted procedures and reducing costs [3]. It is also minimally invasive and comparatively safe. The conclusion from a recently published meta-analysis stated that EUS-FNAC should be included in algorithms for the management of patients with solid pancreatic tumor due to its high accuracy as a diagnostic test [4]. Although EUS-FNAC for diagnosis of solid pancreatic masses is recognized as ‘a nearly perfect procedure [5],’ there are still several flaws that need to be ameliorated. Problematic issues may arise due to limited skills of the endoscopy operator in terms of insufficient yield and targeting-error, misinterpretation and misdiagnosis by pathologists and absence of on-site cytopathologists for adequacy assessment. This study was aimed to evaluate the diagnostic accuracy of EUS-FNAC of the pancreas and to further investigate the reason for incorrect diagnosis by comparison with confirmed histological diagnosis. The reason which we focused on the discrepancy between cytological and surgical specimen diagnosis was to identify the pitfalls that pathologists may face during diagnosis. In some patients, the initial diagnostic cytology specimen may be the only material that has viable tumor cells for diagnosis if the tumor is unresectable or they receive neoadjuvant therapy prior to resection. This situation emphasizes the importance of the accuracy of cytopathologic diagnosis. Furthermore, on-site cytopathologic assessment for adequacy is usually not performed in South Korea for financial reasons [6], making it even more challenging for pathologists in Korea to diagnose cytological specimens. Retrospective examination was performed in this study, correlating cytology-histology diagnosis of pancreatic lesions obtained by EUS-FNAC with several clinicopathologic variables. In doing so, we hope to optimize the accuracy of cytological diagnosis in an effort to improve the care of pancreatic cancer patients.