Pseudomyxoma peritonei pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Parminder Dhingra, M.D. [2]
Overview
The remarkable feature of pseudomyxoma peritonei is that this neoplastic, progressive process often arises from a seemingly benign or well differentiated primary tumor. Pseudomyxoma peritonei may be divided into two pathological subtypes which have aetiological and prognostic significance ( Peritoneal adenomucinosis and Peritoneal mucinous carcinoma).
Pathogenesis
- The pathological process starts with neoplastic transformation of the appendiceal goblet cells and subsequent formation of a primary mucinous tumor.
- While proliferating, tumor cells maintain their constitutive level of mucin expression. As a result, the overall secretion of mucin dramatically rises.
- This is followed by intraluminal accumulation of mucin and eventual development of an appendiceal mucocele.
- A small perforation or rupture of the mucocele is the key event towards the development of pseudomyxoma peritonei through which tumor cells gain access into the peritoneal cavity.
- Lacking cell surface adhesion molecules, the exfoliated tumor cells passively circulate with the peritoneal fluid and redistribute throughout the peritoneal cavity.
- As a result, tumor implants and mucin collections form at the peritoneal fluid re-absorption sites as well as within the dependent portions of the peritoneal cavity to create pseudomyxoma peritonei’s characteristic pattern of the peritoneal dissemination.
- Accumulating mucin increases intraabdominal pressure and compresses visceral organs.
- Furthermore, extensive involvement of the peritoneal surface promotes variable inflammatory and fibrotic responses in the peritoneal environment and hence the development of bowel obstruction as a fatal complication of the disease.[1]
Pathology
- The remarkable feature of pseudomyxoma peritonei is that this neoplastic, progressive process often arises from a seemingly benign or well differentiated primary tumor.
- Pseudomyxoma peritonei may be divided into two pathological subtypes which have aetiological and prognostic significance:
- Peritoneal adenomucinosis
- Peritoneal mucinous carcinoma
- Not all cases may exactly fit into these categories where many of the patients have intermediate or discordant features.
Peritoneal adenomucinosis
- A peritoneal neoplasm composed largely of mucin associated with fibrosis with minimal cytologic atypia and mitoses.
- The primary tumor is generally an adenoma.
Peritoneal mucinous carcinoma
- A peritoneal neoplasm characterised by proliferative epithelium, glands, nests, or individual cells with marked cytologic atypia.
- The primary tumor is a mucinous adenocarcinoma.
Immunohistology
Immunohistochemical markers can help identify the organ of origin. These include positive cytokeratin 20 (CK20), CEA, caudal-type homeobox protein 2 (CDX-2), and MUC2 as well as negative cytokeratin 7 (CK7) and CA125. Of particular interest is the secreted mucin MUC2 that is extensively positive in the patients. Although MUC2 has been suggested as a biological marker of pseudomyxoma peritonei, its significance as a prognostic factor is a matter of controversy.
References
- ↑ Amini, Afshin; Masoumi-Moghaddam, Samar; Ehteda, Anahid; Morris, David (2014). "Secreted mucins in pseudomyxoma peritonei: pathophysiological significance and potential therapeutic prospects". Orphanet Journal of Rare Diseases. 9 (1): 71. doi:10.1186/1750-1172-9-71. ISSN 1750-1172.