Multiple endocrine neoplasia type 2

Multiple endocrine neoplasia type 2 is a rare group of inherited cancer syndromes. Inherited means that it is passed down within a family, and syndrome means that several related problems show up together.

It all comes from a gene called RET. RET is a proto-oncogene, that is, a normal gene involved in the growth of tissues, and it makes a receptor that spans the cell membrane and works as a tyrosine kinase, an enzyme that switches on growth signals. In this syndrome the mutation does not turn the gene off; it leaves it on: a growth switch stuck in the on position from birth. The mutation is germline, meaning it is present in every cell from birth, and it is inherited in an autosomal dominant pattern, which means that receiving it from one parent is enough. The tissues most affected are those that come from the neural crest, a group of cells in the embryo that migrate to form several organs.

That translates into specific tumors. Nearly everyone affected eventually develops medullary thyroid carcinoma, a cancer of the thyroid gland, and up to half develop pheochromocytoma, a tumor of the adrenal gland.