RET and multiple endocrine neoplasia type 2: Oncogenic RET results from either activating mutations or chromosomal rearrangements that produce RET fusion oncogenes, and these are found in a range of cancers, including papillary thyroid carcinoma, medullary thyroid carcinoma, and the multiple endocrine neoplasia types 2A and 2B (MENA2A and MENA2B) [23].