After the cloning of rearranged during transfection (RET) proto-oncogene on chromosome 10q11.2 (Takahashi et al. 1985), its association with various human malignancies was progressively uncovered: first, with finding somatic RET rearrangements (as fusion genes) in up to 20% papillary thyroid cancers (PTC) (Grieco et al. 1990, Viglietto et al. 1995) and then establishing RET germline mutations as the cause of multiple endocrine neoplasia type 2A (MEN2A) (Donis-Keller et al. 1993, Mulligan et al. 1993) and MEN2B (Carlson et al. 1994, Eng et al. 1994, Hofstra et al. 1994). The gene discussed is RET; the disease is multiple endocrine neoplasia type 2A.