Summary Endoscopic ultrasound fine needle aspiration (EUS FNA) is an established and recommended technique for diagnostic of solid pancreatic masses. The accuracy of the technique depends on the operator experience, lesion type and location, type of procedure sedation as well as procedure related technique factors (presence of elastography or contrast enhanced imaging, needle diameter, presence of stylet, use of suction and type of suction, the number and method of "to and fro" movements, the number of passes and the presence of a cytopathologist in the examination room). The relationship between the "to and fro" movement and the EUS FNA yield in solid pancreatic masses has only been explored in the literature in a subjective fashion, without accurately measuring the needle acceleration. Recently, a simple electronic sensor device connected by Bluetooth to a phone, has been proposed for teaching and research purposes. Among its sensors, it includes an accelerometer which can measure the instant scalar acceleration of an object and transmit it to the connected phone. By attaching this device to the EUS FNA needle, the investigators can accurately measure the instant scalar acceleration of the "to and fro" movements. The investigators propose a prospective, multicenter, randomized, crossover study on 51 patients with solid pancreatic masses to compare an EUS FNA "fast" sampling technique in which the needle acceleration is higher than 1 g to a "slow" technique where the needle acceleration is lower than 1g. The primary objective of the study is to compare the tissue acquisition rates and the histological diagnosis accuracy between the 2 methods "fast" and "slow". The secondary objectives of the study are to compare the cellularity and quality scores of the obtained specimens between the 2 methods. Another secondary objective is to find a linear relationship between the needle acceleration and the EUS FNA yield (histological diagnosis, sample cellularity and adequacy).