Diagnosis: Diagnosis of MEN1 could be (i) clinically established if a patient develops two or more MEN1 associated tumours (pituitary and parathyroid adenoma, pancreatic neuroendocrine tumour); (ii) by the presence of one characteristic MEN1 tumour and one first-degree relative with confirmed MEN1 mutation or (iii) due to family cascade genetic screening in asymptomatic carriers [77]. This evidence concerns the gene MEN1 and parathyroid gland adenoma.