Mucinous ovarian cancers were sporadically shown to harbor mutations in ring finger protein 43 (RNF43), phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha, phosphatase and tensin homolog, cadherin 1, E74-like ETS (E-twenty-six) transcription factor 3 (ELF3), AT-rich interaction domain 1A, GNAS (Guanine Nucleotide Binding Protein G Protein, Alpha Stimulating Activity) complex locus, G protein subunit alpha 11 (GNA11), forkhead box L2, FGFR2, serine/threonine kinase 11 (STK11), β-catenin (also known as catenin β-1, CTNNB1), and SMAD family member 4 (SMAD4) [39,50,54,55,56]. The gene discussed is SMAD4; the disease is ovarian cancer.