Cytological Evaluation of Pancreatic Lesions and Reclassification of Aspiration Cytology Smears Based on the Papanicolaou Society of Cytopathology Reporting System: A Cross-sectional Study

Introduction: Pancreatic malignancies are a challenging group of neoplasms with a grave prognosis due to late diagnosis. Endoscopic Ultrasound (EUS)-guided FineNeedle Aspiration Cytology (FNAC) techniques are commonly used as screening tests for early diagnosis of pancreatic malignancies. Standardised guidelines for reporting pancreatic cytology specimens are crucial as discordance between cytological and histopathological diagnosis can affect prompt patient management. The present study aimed to study the cytomorphological features in pancreatic FNAC specimens and to reclassify the smears according to Papanicolaou Society of Cytopathology (PSC) reporting guidelines. Aim: To recategorise the pancreatic aspiration cytology smears according to PSC reporting guidelines. Materials and Methods: This was a cross-sectional study involving all Endoscopy/CT-guided FNAC smears of pancreatic lesions during the period January 2018 to February 2022 in the Department of Pathology, Government Medical College, Kozhikode, Kerala, India. Clinical and cytological features were studied and patients were followed-up over a minimum period of six months. The cytomorphological features were studied in the FNA smears and included cellularity, predominant architectural pattern, nuclear features including nuclear size, degree of anisonucleosis, nuclear contour, nuclear crowding, nuclear chromatin texture, presence of nuclear cleft and inclusions and size of nucleoli, mitotic activity, and nature of background. These features in the FNAC smears of histologically proven malignant cases were compared with those of histologically proven non malignant cases. The cases were recategorised according to PSC reporting scheme. The results were tabulated and analysed using Statistical Package for Social Sciences (SPSS) version 26.0 for Windows. Risk Of Malignancy (ROM) was calculated for each diagnostic cytologic category. Measures of diagnostic accuracy including sensitivity, specificity, positive predictive value and negative predictive value were calculated. The quantitative variables were expressed as mean or median with interquartile range. Qualitative variables were expressed as percentages. The statistical association between variables were analysed using Chi-square test. Results: The study included a total of 147 cases of pancreatic FNAC smears. The most common diagnostic category was Category I which constituted 49.7%, followed by Category VI (17%), Category V (10.9%), Category IV- NeoplasticOthers (9.5%), Category III (9.5%) and Category II (3.4%). No cases were reported as Category IV-neoplastic- Benign. Histopathology follow-up was available for 66 cases. A total of 39 lesions were found to be malignant, while 27 were found to be non malignant. Most common malignant diagnosis was adenocarcinoma (89.7%), followed by poorly-differentiated carcinoma (5.1%) and neuroendocrine carcinoma (5.1%). The ROM for category I, III, IV-neoplastic-others, V and VI were found to be 30%, 25%, 7.69%, 81.81% and 100%, respectively. ROM could not be assessed for category II, as no histopathology follow-up was obtained for these lesions. Sensitivity, specificity, positive predictive value and negative predictive value were found to be 87.18%, 48.14%, 70.83% and 72.22%, respectively. Of the 66 cases with histopathology follow-up, 56 cases had proper cytologic cellular diagnostic yield. Cytomorphological features which were found to be having a statistically significant association in patients with malignant histopathological diagnoses include cellular discohesion, nuclear crowding, marked nuclear enlargement with nuclear pleomorphism, irregular nuclear contour, nuclear chromatin clumping, presence of macronucleoli and necrosis. Conclusion: Cytological techniques are minimally invasive techniques which, along with radiological and molecular techniques, can be used as an important diagnostic tool for diagnosis of pancreatic carcinomas. Proper use of standardised reporting guidelines can increase diagnostic accuracy and can help in risk stratification and early management of these patients.