Results of Molecular Testing in Pancreatic Cystic Lesions: Experience from a Tertiary Care Center

Summary: Introduction: Pancreatic cystic lesions can be challenging to diagnose on cytology due to limited cellularity. Multiple studies have examined the role of ancillary testing on pancreatic cyst fluid (PCF), with molecular testing demonstrating higher sensitivity and specificity. We aim to evaluate the utilization of molecular testing and to correlate the findings with cytologic diagnosis, biochemical findings and surgical follow-up. Materials and Methods: Cases of pancreatic cysts that underwent cytologic examination in 2022 were retrieved from our pathology database. Demographics, cyst location/size, cytologic diagnosis and SFU were obtained from chart review. Biochemical assays (CEA, amylase) and results of Interpace molecular analysis on PCFs were recorded. Results: Our study comprised of 150 cases with female: male ratio of 1.3:1. Location of the lesions were recorded in 128 cases: head (38%, n=48), body (31%, n= 40), tail (23%, n=30), neck (4%, n=5) and uncinate (4%, n=5). Size of the lesions were recorded in 71 cases, with majority (73%, n=52) measuring ≤3 cm. Cytologic diagnoses were categorized as non-diagnostic (ND; n=23), negative for malignancy (NM; n=96), atypical (n=15), positive for neoplasm (n=13) and positive for malignancy (n=3) [Table 1]. 42% of cysts (n=63) underwent biochemical testing only, while 15% (n=22) had both biochemical and molecular analysis. Molecular alterations were detected in 45% (10/22) of the total cohort and in 41% (7/17) of cases reported as ND or NM (Table 2). Only 7% of cases (10/150) underwent surgery (Table 3), with one case having prior PCF analysis. On cytology this case was reported as NM; subsequent PCF analysis demonstrated a KRAS mutation and SFU showed intraductal papillary mucinous neoplasm. Conclusions: Though only 15% of cases in our study underwent molecular testing, alterations were identified in a substantial number of cases. Biochemical analysis and molecular studies helped better characterize these lesions as neoplastic processes. Surgical resection is not influenced by ancillary studies, as only 1 case harboring mutation was resected. This case was reported as NM on cytology but, harbored KRAS mutation on PCF analysis and was diagnosed as neoplastic on resection. Considering that 79% of cases within our study were reported as ND or NM, utilizing molecular testing would help classify these lesions more accurately. More cases are currently being analyzed to improve our data, which is limited by a low number of cases with SFU.