Liver metastases (MTS) are the main cause of death for patients affected by colorectal carcinoma (CRC) and pancreatic ductal adenocarcinoma (PDAC), thus representing the major unmet clinical need for these malignancies. Based on preliminary and published data, the investigators hypothesize that innovative immune, gene and cell therapy approaches might overcome the tolerogenic liver microenvironment and represent powerful therapeutic tools for liver MTS of PDAC and CRC. The investigators have therefore planned an observational clinical study to enroll distinct cohorts of patients (i.e., metastatic CRC, metastatic and non-metastatic PDAC) and finely characterize, through integrated state-of-the-art -omics, the immune and non-immune microenvironment of their primary tumor and/or liver metastases as well as correlate changes in the activation status and phenotype of peripheral blood leukocytes. Healthy volunteers will be enrolled as negative controls. The investigators aim at identifying: i) actionable tumor associated antigens (TAAs) and local immune suppressive and regulatory pathways; ii) biological parameters for early diagnosis of relapse; iii) the effect of therapies on the shaping of anti-tumor immune responses. Data collected will be instrumental for the generation of novel advanced therapy medicinal products (ATMPs). Indeed, this protocol is part of a multi-partner translational program, supported by the AIRC 5 per Mille 2019 grant, focused on the development, validation and implementation for clinical testing of ATMPs to ameliorate the cure of CRC and PDAC and possibly help the study of other solid tumors. Moreover, the systematic and long-term follow-up of enrolled patients will possibly point at early predictors of differential prognosis and patients' categories eligible for tailored therapies, including those with the novel ATMPs.