Pseudomyxoma peritonei pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Nima Nasiri, M.D.[2]

Overview

Pseudomyxoma peritonei (PMP) is a rare tumor known for its production of abundant mucinous ascites in the abdominal cavity. It can have a mass impact on vital organs such as spleen, pancreas, and kidney. Pseudomyxoma peritonei may be divided into two pathological subtypes: peritoneal adenomucinosis and peritoneal mucinous carcinoma.

The pathogenesis of the disease is related to biomarkers and molecular genetic alterations.

Immunohistochemical markers and genetic alterations involved in the pathogenesis of pseudomyxoma peritonei include:^[1]
- CK 20
- CDX2 and MUC2 are found to be positive in these tumors.
- KRAS mutation and loss of heterozygosity in some gene loci.
- Losses of alleles in chromosomes 18q, 17p, 5q.

Pseudomyxoma peritonei may be divided into two pathological subtypes:^[2]

Disseminated peritoneal adenomucinosis (DPAM) which has charracteristic features of the following:
- Peritoneal lesions with abundant extracellular mucin
- Proliferative mucinous epithelium
- Less mitotic activity as compared with peritoneal mucinous carcinomatosis
Peritoneal mucinous carcinomatosis (PMCA) which is characterized by:
- Peritoneal lesions having more abundant mucinous epithelium
- Characteristic cytologic features of carcinoma, with high mitotic activity.

Immunohistochemical markers can help identify the organ of origin.

The tumor is positive for cytokeratin 20 (CK20), CEA, caudal-type homeobox protein 2 (CDX-2), and MUC2 as well as negative cytokeratin 7 (CK7) and CA125.
Studies have shown that mucin MUC2 and MUC5AC is extensively positive in pseudomyxoma peritonei patients. ^[3]

↑ Szych C, Staebler A, Connolly DC, Wu R, Cho KR, Ronnett BM (June 1999). “Molecular genetic evidence supporting the clonality and appendiceal origin of Pseudomyxoma peritonei in women”. Am. J. Pathol. 154 (6): 1849–55. doi:10.1016/S0002-9440(10)65442-9. PMC 1866622. PMID 10362811.
↑ Ronnett BM, Zahn CM, Kurman RJ, Kass ME, Sugarbaker PH, Shmookler BM (December 1995). “Disseminated peritoneal adenomucinosis and peritoneal mucinous carcinomatosis. A clinicopathologic analysis of 109 cases with emphasis on distinguishing pathologic features, site of origin, prognosis, and relationship to “pseudomyxoma peritonei““. Am. J. Surg. Pathol. 19 (12): 1390–408. PMID 7503361.
↑ Nonaka D, Kusamura S, Baratti D, Casali P, Younan R, Deraco M (October 2006). “CDX-2 expression in pseudomyxoma peritonei: a clinicopathological study of 42 cases”. Histopathology. 49 (4): 381–7. doi:10.1111/j.1365-2559.2006.02512.x. PMID 16978201.