<p>Pancreatic neuroendocrine tumours (PanNETs) are well-differentiated neoplasms that present with a variable clinical picture and prognosis. This makes accurate classification essential for guiding treatment and assessing outcomes. The current WHO classification system categorises PanNETs according to their proliferative activity. A morphological assessment combined with immunohistochemistry is central to the diagnosis, as it confirms neuroendocrine differentiation and rules out differential diagnoses. Nevertheless, panels targeting neuroendocrine and lineage-specific markers can enhance diagnostic confidence. Both histological and molecular predictive biomarkers are playing an increasingly significant role in tumour classification, prognosis and therapeutic decision-making. This review highlights the current morphological and immunohistochemical criteria for PanNET diagnosis and emphasises the growing importance of predictive biomarkers.</p>