Endoscopic ultrasound-guided fine needle aspiration of accessory spleen: Cytomorphologic features and diagnostic considerations.

Abstract

Accessory spleen/or splenule (AS) can involve pancreas/or peripancreatic tissue and present as a mass-forming lesion, and on imaging studies, it stimulates concern for a neoplastic process. The current study reported the largest cohort of AS cases evaluated by endoscopic ultrasound-guided fine needle aspiration (EUS-FNA). We retrospectively reviewed our data base system for cases underwent EUS-FNA for pancreatic/or peripancreatic lesions, with "AS" in diagnosis or in note/or with a clinical concern in the history, from January 2010 to August 2019. Corresponding cytology slides were re-reviewed to identify the key cytomorphologic features. We identified 25 AS cases from 15 female and 10 male patients with a mean age of 55 years. Most patients presented with non-specific clinical symptoms or were identified as an incidental mass lesion. Majority of the lesions were located in or around the pancreatic tail region (68%) while the remainder in perisplenic region (32%). Rapid on-site evaluation (ROSE) was performed in nearly half of the cases (48%). Cytologically, AS shows a mixed population of medium to small-sized lymphocytes, clusters of lymphoid cells (LC), prominent vascularity (PV), scattered mixed inflammatory cells including eosinophils, and large platelet aggregates (LPAs). Among them, LC (P = .0079), PV and LPAs were the most helpful features for cytological diagnosis. AS is a benign entity and may pose a diagnostic challenge due to its resemblance to a neoplastic process on imaging studies. EUS-FNA is an important tool to recognize AS by identifying its key cytologic features, thus may help to avoid unnecessary surgical management.