Higher magnification from a case of low-grade pseudomyxoma peritonei (Diffuse Peritoneal Adenomucinosis) showing a strip of mucinous epithelium totally lacking cytologic atypia. In a recent review paper, Chua et al examined the outcome of almost 2,300 patients with pseudomyxoma peritonei treated over an 18-yr period from 16 institutions worldwide (J Clin Oncol 30:2449-2456, 2012). The site of primary tumor in most cases was the appendix. Five year survival was 81% for low-grade tumors (Diffuse Peritoneal Adenomucinosis) and 59% for high-grade tumors (Peritoneal Mucinous Carcinomatosis). Some studies have reported a 5-yr survival rate of <10% for high-grade tumors.