Diffuse type gastric cancer is currently subdivided into signet-ring cell carcinoma (SRCC) and non-SRCC referred to as poorly cohesive carcinoma not otherwise specified (PCC-NOS). Although these subtypes are considered to be independent, they often co-exist in the same tumors, raising a question whether they clonally differ or not. To tackle this question, we established an experimental platform for human diffuse gastric cancer that enables accurate modeling of histological subtypes.