Neoplasms of the Appendix

Abstract

Background: Neoplasms of the vermiform appendix are rare. They comprise a heterogeneous group of entities requiring differentkinds of treatment.

Methods: This review is based on publications retrieved by a selective literature search in the PubMed, Embase, and Cochranedatabases.

Results: 0.5% of all tumors of the gastrointestinal tract arise in the appendix. Their treatment depends on their histopathologicalclassification and tumor stage. The mucosal epithelium gives rise to adenomas, sessile serrated lesions, adenocarcinomas,goblet-cell adenocarcinomas, and mucinous neoplasms. Neuroendocrine neoplasms originate in neuroectodermal tissue. Adenomasof the appendix can usually be definitively treated by appendectomy. Mucinous neoplasms, depending on their tumorstage, may require additional cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemoperfusion (HIPEC). Adeno -carcinomas and goblet-cell adenocarcinomas can metastasize via the lymphatic vessels and the bloodstream and should thereforebe treated by oncological right hemicolectomy. Approximately 80% of neuroendocrine tumors are less than 1 cm in diameterwhen diagnosed and can therefore be adequately treated by appendectomy; right hemicolectomy is recommended if the patienthas risk factors for metastasis via the lymphatic vessels. Systemic chemotherapy has not been shown to be beneficial forappendiceal neoplasms in prospective, randomized trials; it is recommended for adenocarcinomas and goblet-cell adenocarcinomasof stage III or higher, in analogy to the treatment of colorectal carcinoma.

Figure 1:

Aspects of low-grade mucinous neoplasms of the appendix (LAMN) a) Histologic image of LAMN, HE staining; typical lamina propria replaced by villous proliferation of mucinous, mildly atypical epithelia that border on fibrosed connective tissue b) Computed tomography (CT) scan LAMN (arrow) without any indication of Pseudomyxoma peritonei (PMP) c) Intraoperative finding of Pseudomyxoma peritonei with mucin deposits on the hepatic capsule as well as on the lesser and greater omentum

Figure 2

Flow chart of recommended therapy of low-grade mucinous neoplasms of the appendix. HAMN, high-grade mucinous neoplasms; HIPEC hyperthermic intraperitoneal chemoperfusion; LAMN, low-grade mucinous neoplasms; PMP, Pseudomyxoma peritonei

Figure 3

Flow chart of therapy for neuroendocrine tumors of the appendix *Risk factors: R1 resection, angioinvasion, infiltration of mesoappendix > 3 mm and KI-67 > 2 %; NET, neuroendocrine tumor