Potential actionable targets in appendiceal cancer detected by immunohistochemistry, fluorescent in situ hybridization, and mutational analysis

Cancers arising from the appendix are rare. In reports of appendectomy specimens, the incidence of malignancy has been reported to be between 0.58% to 0.9% (1,2). The histological spectrum is quite varied, with recent reports through large database studies indicating adenocarcinoma being the most common subtype (3,4). Other histological variants include carcinoid or neuroendocrine and a mixed histology tumor of both carcinoid and adenocarcinoma subtype termed goblet cell carcinoma (5). Finally, another epithelial variant of appendiceal cancer is pseudomyxoma peritonei (PMP), a mucinous neoplasm that clinically presents as gelatinous ascites (6,7). Due to the rarity of these malignancies limited prospective trials exist guiding management. In general, treatment involves surgery for all histological subtypes. For patients with carcinoid appendiceal tumors and goblet cell, appendectomy may be considered in lesions less than 2 cm in size. For lesions 2 cm or more or those with higher grade carcinoid or lymph node involvement right colectomy is indicated (8). For patients with appendiceal adenocarcinoma (<2 cm in size), there is great debate on pursuing simple appendectomies versus hemicolectomy and frequently depends upon opinion (9-11). In patients with PMP, standard treatment involves repeated surgical debulking for symptomatic disease (12). Some clinicians also add intraperitoneal hyperthermia (IPH) treatment or intraperitoneal hyperthermic chemotherapy (IPHC) (13-15)