Advanced sporadic MTC are characterized by a high prevalence of RET somatic mutations. In particular the M918T is the most frequent mutation but also small deletions/insertions (complex mutations can be present. In some cases more than one RET mutation can occur. K- or H-RAS mutations are also present even if at a lower frequency. RET and RAS mutations are mutually exclusive. Cases with multiple or complex mutations have a worse outcome. (By Drs. Rossella Elisei and Cristina Romei, http://jmg.bmj.com/content/early/2016/07/28/jmedgenet-2016-103833 )