Carcinoma, Signet Ring CellAdenocarcinoma, MucinousStomach NeoplasmsAppendiceal NeoplasmsUmbilicusMicrosatellite InstabilityCarcinomaGastrectomyRare DiseasesMucinsImmunohistochemistryAdenocarcinomaProto-Oncogene Proteins B-rafPeritoneal NeoplasmsCadherinsAlcian BluePyloric AntrumEndoscopy, GastrointestinalColorectal NeoplasmsNeoplasm Staging