Multiple endocrine neoplasia

[surgery1991]

Multiple endocrine neoplasia type 1 (MEN type 1)

️Also called Wermer syndrome, It is an uncommon hereditary disorder of endocrine glands affecting about 30 in 100000 of population each year and it is inherited as autosomal dominant with almost 100% penetrance (i.e almost everyone who carry the mutation will manifest the disease).

️The mutation is a loss of function mutation affecting the tumor suppressor gene Menin 1 located on chromosome 11, there is an exhausting list of different mutations affecting this gene but this is not clinically important as the manifestations are the same for different mutations (No genotype-phenotype correlation), this is not the case for MEN type 2 which shows strong genotype-phenotype correlation, which means that a particular mutation affecting the involved gene produce different clinical manifestations and therefore the specific mutation in MEN type 2 is important whereas in MEN type 1 is not.

️The most common clinical manifestation of MEN type 1 is hyperparathyroidism, which essentially occur in all patients (95-100%), the most common manifestation of primary hyperparathyroidism whether related to MEN type 1 or sporadic, is kidney stones.

️Parathyroid pathology can be an adenoma or hyperplasia, but the important point is that it affects multiple parathyroid glands and this will affect the treatment strategy.

️Indications of surgery in primary hyperparathyroidism are essentially the same on sporadic cases, for short, any clinical impact is an indication including kidney stones, abdominal pain, reduced bone mineral density... Etc.

️When surgery is indicated, bilateral neck exploration is required, this is unlike sporadic cases which are most commonly caused by a single adenoma in which minimally invasive parathyroidectomy is employed, options are between subtotal parathyroidectomy (three and a half glands are removed) and total parathyroidectomy with implantation of some parathyroid tissue in the forearm, additionally routine trans-cervical thymectomy is required as ectopic parathyroid tissue in the thymus is common and if left behind can lead to recurrence, moreover, a rare but serious manifestation of MEN type 1 is thymic carcinoid tumor which is often malignant and aggressive and this can justify routine thymectomy.

️The next most common manifestation is pancreatic endocrine tumor which affect 50-80% of all cases, they can be non-functioning, or functioning, the most common functioning tumor is gastrinoma (note that in sporadic cases the most common pancreatic endocrine tumor is insulinoma) followed by insulinoma, pancreatic endocrine tumors are the most common cause of death in patients with MEN type 1.

️Most common site of gastrinomas in MEN type 1 (as well as in sporadic cases) is the duodenum they are often multiple and as such are usually treated by pylorus preserving pancreatoduodenectomy, tumors in the body or tail can be managed by distal pancreatectomy, insulinomas are usually managed by enucleation.

️Pituitary tumors affect 30-60% of cases, most common pituitary tumors in MEN type 1 are prolactinomas or non functioning adenomas, they are usually microadenomas and can usually be managed medically.

️Adrenal tumors in MEN type 1 are common, and can affect up to 50% of cases, they are usually non functioning adenomas, and rarely adrenocortical carcinomas or even pheochromocytomas, laparoscopic resection is indicated for tumors 4 cm or more, when likelihood of malignancy is high open surgery is preferred to laparoscopic surgery, because risk of tumor spillage is lower when open surgery is advocated.

️Other rare manifestations of MEN type 1 include carcinoid tumors of lungs, gastrointestinal tract and thymus.

Summary:

-Can be remembered as 3 P's :Parathyroid, pancreatic and pituitary endocrine tumors.

#Endocrine

[surgery1991]