PrognostIc and Predictive Factors in Unresectable Locally Advanced NEC and MANEC

Inclusion Criteria: * Histological diagnosis of unresectable locally advanced or metastatic NEC or MANEC confirmed by an expert-pathologist * EP-primary site (included unknown primary site * Age \> 18 years * Signed written informed consent * Performance status ≤2 * Available tumor tissue (formalin-fixed paraffin-embedded, FFPE) (preferably within 6 months). If the tumor contained in FFPE tissue block cannot be provided in total, sections from this block should be provided that are freshly cut. Preferably, 25 slides should be provided (minimum of 15 slides). If tumor tissue is not available, patients should be willing to undergone to a new biopsy. Exclusion Criteria: * Diagnosis of well-differentiated NEN (G1, G2, G3) * Collision tumors * Cytological diagnosis of NEC or MANEC or not availability of tumor tissue for pathological analysis. * Concurrent neoplastic disease (e.g. Advanced breast or prostatic cancer in hormonal treatment, hematologic diseases)