Peritoneal Dissemination of Gastrointestinal Tumors

Abstract

The term peritoneal surface malignancy (PSM) applies to a wide range of epithelial or, less frequently, mesenchymal neoplasms that originate from the primitive structure of the peritoneum (primary PSM), or spread over the peritoneum as metastases from tumors of intra-abdominal, retroperitoneal, or extra-abdominal organs (secondary PSM). Primary PSMs, including peritoneal mesothelioma and primary peritoneal carcinoma, are rare. Peritoneal dissemination of colorectal, gastric, and ovarian cancers, known as peritoneal carcinomatosis (PC), represents the most frequent types of secondary PSM (Treatment of peritoneal surface malignancies, Milan, 2015). As the focus of this monograph, three secondary PSM entities, including colorectal and gastric PCs and the pseudomyxoma peritonei (PMP) syndrome, are revisited in this chapter. Hematogenous and lymphatic metastases of gastrointestinal cancers follow a well-defined pattern of distribution, with the regional lymph nodes and the liver being the initial sites for cancer spread. Peritoneal dissemination is a third mechanism that can result from serosal invasion or visceral perforation by tumor, or may develop as an iatrogenic complication following diagnostic or therapeutic interventions. Distinctions in gene expression profiles and the involvement of certain molecular pathways are believed to determine the metastatic site of gastrointestinal cancer (peritoneum versus liver) (Varghese et al., Annals of Surgical Oncology 14: 3460–3471, 2007). The past assumption that peritoneal dissemination is a random process has been challenged by meticulous observations that have identified different patterns and mechanisms governing the dissemination of tumor cells. In this regard, anatomic site of the primary tumor, histologic type of tumor, changes in intra-abdominal pressure, gravity, peritoneal surface motion (peristalsis), peritoneal fluid resorption, viscosity and volume of fluid within the abdomen, peritoneal adhesions, and fibrin entrapment are among factors that affect the pattern of spread (Carmignani et al., Cancer and Metastasis Reviews 22: 465–472, 2003). Also classified as a secondary PSM with an appendiceal primary origin, PMP represents the prototype for the peritoneal neoplasms associated with mucin secretion and accumulation. PSM is usually associated with poor prognosis regardless of the origin of the primary tumor. By virtue of the recent advances, however, the treatment paradigm has shifted from palliative to curative (Sugarbaker, Langenbeck’s Archives of Surgery 384: 576–587, 1999a; Esquivel, Surgical Oncology Clinics of North America 21: xv–xviii, 2012; Mohamed et al., Current Oncology 18: e84–e96, 2011). The classification of PSM is outlined in Table 1.1.