Prognostic Factors: Molecular Pathway – Tumour Suppressor Gene (MEN1)

Multiple Endocrine Neoplasia type 1 (MEN1) is the most prevalent inherited cause of neuroendocrine tumours (NETs), which are part of the MEN1 triad with primary hyperparathyroidism and pituitary adenomas. MEN1 is an autosomal dominant disorder with a nearly complete penetrance, due to germline inactivating mutations in the MEN1 gene. Compared with sporadic cases, MEN1-NETs are characterised by an earlier onset, frequent multiplicity within and across neuroendocrine tissues/organs, and potential malignancy. As a consequence, prognostic factors identified in a sporadic setting may not correctly apply to MEN1-NETs, surgical indications may differ, and NETs still represent a major cause of death in affected patients. Expert clinical guidelines rather than evidence-based guidelines have been developed to optimize early tumour detection and management, but open issues remain. Yet, the follow-up of MEN1 patients in real life remains challenging, especially in young patients (<20 year), in whom there is increasing evidence of asymptomatic NETs.