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

ABSTRACT

INTRODUCTION: 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. PATIENTS AND METHODS: 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. RESULTS: This study included 25 patients (24 were women). Patients' mean age was 33.7 years (range 12-78 years). The most common symptom was abdominal pain. SPN was an incidental finding in 52% of the patients. The mean lesion size was 4.3 cm (range 1.2-11.4 cm), 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 ß-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. CONCLUSIONS: 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 ß-catenin, CD 10, CD99 and PR expression must be included in the IHC panel for diagnostic confirmation of SPNs using EUS-FNA biopsy specimens.