Pseudomyxoma Peritonei (PMP) is a rare kind of cancers whose incidence is about one out of million people. Since researches of PMP had not sufficiently been progressed so far, characteristics and details of generation mechanism of PMP have not been elucidated, and it is difficult to specify the primary site of PMP. In this research, focusing on PMP, we attempt the gene expression data analysis based on a self-organizing map (SOM).