“…Probably, different variations somewhere in the ret gene or in flanking genes could account for the different phenotypes (MEN 2A versus FMTC) in families with the same mutations (Goodfellow & Wells 1995). In each familial MEN 2A case the ret gene mutations in affected patients have been described in exon 10, in one of four cysteine codons (609, 611, 618 and 620) and exon 11, at the cysteine codon 634, at the boundary of the extracellular and transmembrane domains harboring a cysteine rich region (Table 1) (Marsh et al 1994, Schuffenecker et al 1994, Xue et al 1994, Zedenius et al 1994, Gagel et al 1995, Komminoth et al 1995, Landsvater et al 1996, Mulligan et al 1995. Two newer mutations in exons 13, codon 768, and 14, codon 804, have been described in families with FMTC (Eng et al 1995a, Bolino et al 1995.…”