Diagnosis of pancreatic solid pseudopapillary neoplasms using cell‐blocks and immunohistochemical evaluation of endoscopic ultrasound‐guided fine needle aspiration biopsy specimens

Abstract

Preoperative diagnostic imaging of pancreatic solid pseudopapillary neoplasms (SPNs) is challenging. A few studies have investigated the role of endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) for the diagnosis of SPN. We investigated the diagnostic yield of cell-blocks and immunohistochemistry (IHC) for SPN using EUS-FNA specimens without cytological evaluation. We retrospectively analysed the histopathology records of patients with suspected SPN, who underwent EUS-FNA biopsy between January 1997 and January 2020. Diagnosis based on cell-blocks (haematoxylin-eosin staining with complementary IHC) was compared with the definitive surgical diagnosis. This study included 25 patients (24 were women). Patients' mean age was 33.7years (range 12-78years). The most common symptom was abdominal pain. SPN was an incidental finding in 52% of the patients. The mean lesion size was 4.3cm (range 1.2-11.4cm), and the most common endosonographic features included solid-cystic (56%) or solid (40%) tumours. Final diagnoses included SPNs (n = 23) and non-functioning neuroendocrine tumours (n = 2). The overall accuracy of EUS-FNA was 80%. Tumour cells showed immunopositivity for β-catenin, CD10, CD99 and progesterone receptor (PR) in 93.7%, 87.5%, 83.3% and 66.6% of patients, respectively. No SPN showed immunopositivity for chromogranin A. Intention-to-diagnose analysis showed that the diagnostic accuracy of EUS-FNA for SPNs using cell blocks and complementary IHC without cytological evaluation was fairly good. Evaluation of β-catenin, CD 10, CD99 and PR expression must be included in the IHC panel for diagnostic confirmation of SPNs using EUS-FNA biopsy specimens.