Chapter 105: Appendiceal Neoplasms

BACKGROUND

The appendix is a rare site of malignancy, with a large variety of histologic subtypes. Reviews of large series of appendectomies reveal appendiceal neoplasms in nearly 0.7% to 0.9% of cases.^1,2 Even with the large number of appendectomies performed annually in the United States, appendiceal malignancies remain a rare entity, comprising less than 1% of colorectal malignancies. The age-adjusted risk of development of appendiceal cancer is estimated at just 0.12 cases per 1,000,000 per year.^3,4 The rarity of the diagnosis makes database reviews and small series the primary source of information regarding frequency of diagnoses and outcomes. McCusker was the first to conduct a review of the SEER database, reviewing 2117 appendiceal malignancies reported to SEER between 1973 and 1998.⁴ Additional SEER reviews based on the same population but extending the time interval slightly have been published by McGory and Turaga, revealing fairly similar results.^5,6

While the SEER database provides no information regarding the clinical presentation of patients with appendiceal malignancies, large case series confirm that the diagnosis is seldom made prior to surgery. Patients with appendiceal neoplasms commonly present with signs and symptoms of appendicitis. The diagnosis is often not suspected intraoperatively, and a finding of cancer may not be made until the pathologic analysis. While the majority present with presumed appendicitis, a sizable minority of patients are diagnosed via imaging performed for abdominal pain or as incidental findings in the workup of other complaints.

Benign neoplasms represent between 20% and 40% of appendiceal malignancies, and include leiomyomas, neuromas, and lipomas.⁷ Lesions of intermediate behavior include low-grade mucinous neoplasms as well as typical carcinoid tumors. More aggressive malignant neoplasms include atypical carcinoid, adenocarcinoma, and goblet cell carcinoid. The 7th edition of the AJCC staging manual introduces separate staging systems for typical carcinoids and all other appendiceal tumors. However, the behavior and management of appendiceal neoplasms vary widely. Due to their differing features, prognosis, and treatment they will be discussed individually in this chapter, but a general classification scheme is shown in Table 105-1. Pseudomyxoma peritonei, the term used to describe peritoneal dissemination of a mucus-producing malignancy, may originate from appendiceal malignancies, and is included in the types of appendiceal cancer discussed in this chapter.

CARCINOID

The term “karzinoid” was coined by the German pathologist Sigfried Oberndofer, and reflected his understanding that the behavior of carcinoid tumors was less aggressive than that of typical adenocarcinoma.⁸ While carcinoid tumors develop not only in the digestive tract but also within the lung, the appendix is disproportionately represented as a ...