25th May 2025

Multiple neuroendocrine neoplasia (MEN)

MEN is an autosomal dominant disorder which is defined by multiple neuroendocrine tumours.  MEN is caused by the RET oncogene mutation. The most common tumours associated are listed below however any neuroendocrine tumour can present as part of the condition including the pancreas, duodenum, lung and thymus. Patients identified at high risk of MEN tumours due to family history should be offered annual biochemical and radiological screening under MDT review. Treatment consists of treating the individual tumours. MEN1 is caused by a MEN gene mutation whereas MEN2 is caused by RET oncogene mutation. MEN is diagnosed by genetic testing either through surveillance due to family screening or if it suspected when someone develops a MEN tumour, such as a parathyroid, pancreatic neuroendocrine tumour or pituitary gland tumour. These tumours would present as expected –for example, with hyperparathyroidism or as a functioning or non-functioning pituitary tumour. Investigations would include bloods for calcium and hormone levels and imaging such as CTCAP and MRI pancreas. 

MEN1: parathyroid adenoma (90%), pancreas (30-70%), pituitary (30-40%) 

MEN2A: medullary thyroid (90%), phaeochromocytoma (50%), parathyroid adenoma (20-30%) 

MEN2B: medullary thyroid (>90%), phaeochromocytoma (40-50%), mucosal neuromas, marfanoid features

Von-Hippel-Landau disease and neurofibromatosis also inherited disorders associated with the development of neuroendocrine tumours.

Von-Hippel-Landau: presents with haemangioblastomas in the CNS and retina, phaeochromocytoma, increased risk of renal cell carcinoma and liver and renal cysts. 

Neurofibromatosis 1 (NF1): presents in late childhood with characteristic café-au-lait spots, cutaneous neurofibromas, plexiform neurofibromas, phaeochromocytoma, as well as cardiovascular and neurological disorders.

Neurofibromatosis 2 (NF2): significantly less common and presents in adulthood. It is characterised by bilateral vestibular neuromas/Schwannomas which can lead to deafness and hearing loss.