Historically, MEN2 syndrome has been classified into three distinct variants: MEN2A (OMIM 171400), which occurs in 80% of all hereditary cases7, 8, familial medullary thyroid cancer (FMTC) (OMIM 155240), arising in up to 57% of all hereditary cases, and MEN2B (OMIM 162300), in approximately 5% of all hereditary MTCs9. Here, RET is linked to familial medullary thyroid carcinoma.