Pancreatic ductal adenocarcinoma (PDAC) complexity, where genetic, stromal, and immunological factors all interact with each other, is responsible for the overall poor response of PDAC to chemotherapeutic agents, making this a lethal disease. The investigators hypothesize that: (i) dissection of genetic, stromal, and immunological factors on endoscopic ultrasound fine needle biopsy (EUS-FNB) tissue samples from unresectable PDAC patients' will allow to determine prognostic factors in this patient population; (ii) treatment response and acquisition of tumor chemotherapy resistance could be related to genetic heterogeneity between the primary and metastatic sites and alteration of the molecular profile under drug' selection pressure.