INTRODUCTIONDifferential diagnosis of pancreatic masses is a frequent clinical challenge. Therapeutic decision in this context is mainly based on the ability to establish or exclude malignancy [1] . Although ductal adenocarcinoma is the most frequent cause of pancreatic masses, other neoplasms (e.g. lymphoma, cystic tumours) and benign conditions (e.g. chronic pancreatitis) with different prognoses and treatment options can arise within the pancreas. A histological diagnosis becomes therefore highly relevant for an optimal therapeutic decision [2] . Endoscopic ultrasound (EUS)-guided fine needle aspiration (FNA) has been proved to be a safe and useful method for tissue sampling of intramural and extramural gastrointestinal lesions including the pancreas [3,4] . Cytological study of the materials obtained by FNA allows the evaluation of cellular findings suggestive of malignancy, such as anisonucleosis, nuclear membrane irregularity and nuclear enlargement. Unfortunately, inflammation causes a reactive and regenerative process leading to cellular changes that can be difficult to distinguish from well-differentiated neoplasias. Histological study of tissue samples allows the assessment of tissue architecture and cell morphology, as well as the performance of immunohistochemical analysis [5,6] , thus usually providing with a higher diagnostic accuracy than cytology.Retrieving Abstract AIM: To evaluate the diagnostic accuracy of histological evaluation of pancreatic tissue samples obtained by a modified method for recovering and processing the endoscopic ultrasound (EUS)-guided fine needle aspiration (FNA) material in the differential diagnosis of pancreatic solid masses.
METHODS:Sixty-two consecutive patients with pancreatic masses were prospectively studied. EUS was performed by the linear scanning Pentax FG-38UX echoendoscope. Three FNAs (22G needle) were carried out during each procedure. The materials obtained with first and second punctures were processed for cytological study. Materials of the third puncture were recovered into 10% formol solution by careful injection of saline solution through the needle, and processed for histological study.
RESULTS:Length of the core specimen obtained for histological analysis was 6.5 ± 5.3 mm (range 1-22 mm). Cytological and histological samples were considered as adequate in 51 (82.3%) and 52 cases (83.9%), respectively. Overall sensitivity of both pancreatic cytology and histology for diagnosis of malignancy was 68.4%. Contrary to cytology, histology was able to diagnose tumours other than adenocarcinomas, and all cases of inflammatory masses. Combination of cytology and histology allowed obtaining an adequate sample in 56 cases (90.3%), with a global sensitivity of 84.21%, specificity of 100% and an overall accuracy of 90.32%. The complication rate was 1.6%.
CONCLUSION:Adequate pancreatic core specimens for