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
Pathophysiology
- 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 PMP 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 PMP’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
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
Not all cases fit neatly into these categories, and many patients have intermediate or discordant features.
Immunohistology
Immunohistochemical markers can help to 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 PMP, 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.