Biomarker Study in Pancreatic Neuroendocrine Tumours

Inclusion Criteria: * Age ≥18 years * Informed consent * WHO performance status ≤2 * Progressive disease (as defined by the local investigator) or newly diagnosed disease (defined as prior to medical or oncological intervention except for somatostatin analogue treatment). * Pathology confirmed diagnosis of pancreatic or duodenal neuroendocrine tumour WHO G1-G3. o Exception: In newly diagnosed patients with high suspicion of PNET based on clinical and radiological parameters where tissue sample have not yet been obtained. These patients may be included and subsequently excluded if pathology cannot confirm NET. * Biopsy procedure not associated with inappropriate risk as determined by the responsible physician. Exclusion Criteria: * Patient does not consent * Permanent risk factors for biopsy * Long term treatment with anticoagulant that cannot be temporarily paused without unacceptable risk. * Permanent coagulation disorder * Pregnancy or no contraceptive in fertile women.