In this particular case, contiguous but histologically disparate regions of the tumor comprising crypt cell neuroendocrine carcinoma (a.k.a. goblet cell carcinoid) and classical mucinous adenocarcinoma (Fig 1) harbored distinct SMAD4 mutations, MH2 domain (c.1082G>A) mutation and c.379T>A in the latter, respectively, despite harboring identical mutations of KRAS (c.35G>T) and TP53 (c.742C>T). The gene discussed is KRAS; the disease is colon mucinous adenocarcinoma.