Table 2.

Histopathologic features of epithelial mucinous tumors of appendiceal, colonic, and small bowel origin are designated as disseminated peritoneal adenomucinosis (DPAM) and peritoneal mucinous carcinomatosis (PMCA).

Features	DPAM	PMCA
Primary site	Appendix	Appendix, colon, small intestine
Primary diagnosis	Mucinous adenoma usually in a mucocoele	Mucinous adenocarcinoma
Surgical appearance	Mucinous tumors and mucinous ascites with redistribution	Carcinomatosis with variable amounts of mucinous ascites, redistribution is prominent with large volume of ascites
Peritoneal tumor
• Cellularity	Scant	Moderate to abundant
• Morphology	Abundant extracellular mucin containing simple to focally proliferative mucinous epithelium. There is a single layer of cells	Moderate to abundant extracellular mucin containing extensively proliferative mucinous epithelium or mucinous glands, clusters of cells, or individual cells consistent with carcinoma
• Cytologic atypia	Minimal	Moderate to marked
• Mitotic activity	Rare	Infrequent to frequent
Lymph node involvement	Almost never	Moderate
Liver metastases	Almost never	Very infrequent
Parenchymal organ invasion	Rare (except ovary)	Frequent

Hybrid type tumors show less than 5% of PMCA within DPAM. Mucinous carcinomas are divided into three grades by maintenance or loss of glandular architecture.