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The incidence of appendiceal tumors in the United States is approximately 2500 to 5000 cases per year.1,2 There are two major types of appendiceal neoplasms: nonepithelial neoplasms including neuroendocrine neoplasms (previously referred to as carcinoids) and epithelial neoplasms including mucinous adenocarcinomas, colonic-type adenocarcinomas, goblet cell carcinoids (adenocarcinoid), and signet ring cell carcinomas (Table 120-1). The carcinogenesis, tumor biology, clinical presentation, management, and oncologic outcomes differ among the various tumor subtypes mentioned above. The oncologic outcomes and management strategies for colonic-type adenocarcinomas and signet ring cell carcinomas of the appendix mimic their counterparts within the colon, and will therefore not be discussed in this chapter. Similarly, neuroendocrine neoplasms of the appendix will be considered in a separate chapter.

TABLE 120-1:

Appendiceal Tumors



Mucinous appendiceal neoplasms (MAN) are characterized by abundant extracellular mucin comprising > 50% of the tumor volume. These neoplasms have a high tendency for peritoneal metastases, that may occur from rupture of a mucin-filled appendix harboring a MAN or following transmural invasion of mucin-secreting neoplastic cells from the primary tumor. Peritoneal metastases from MAN are referred to as pseudomyxoma peritonei (PMP), a clinicopathologic entity that is characterized by accumulation of mucinous ascites and mucin-secreting neoplastic epithelial cells within the peritoneal cavity (Fig. 120-1).3,4 PMP of appendiceal origin is thought to be a malignancy of mucin-secreting neoplastic goblet-like cells, since goblet cells are the primary source of mucin production within the normal intestinal epithelium.5

FIGURE 120-1:

A. Ruptured mucinous appendiceal neoplasm (MAN) with dissemination of mucin into the peritoneal cavity (arrowheads represent extravasated mucin; arrow represents dilated appendix harboring a MAN). B. Pseudomyxoma peritonei (PMP) with mucinous tumor deposits encasing the omentum and transverse colon.

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