TY - CHAP M1 - Book, Section TI - Rare GI Tumors A1 - Beard, Rachel E. A1 - Nagle, Deborah A2 - Morita, Shane Y. A2 - Balch, Charles M. A2 - Klimberg, V. Suzanne A2 - Pawlik, Timothy M. A2 - Posner, Mitchell C. A2 - Tanabe, Kenneth K. Y1 - 2018 N1 - T2 - Textbook of Complex General Surgical Oncology AB - In this section we discuss oncologic entities of the lower gastrointestinal (GI) tract, comprising the appendix, colon, rectum, and anus, which are less frequently encountered in surgical practice. These pathologies are distinct tumors that are related only by their common location in the lower GI tract and the infrequency of their occurrence. The lower GI tract tumors to be discussed, in descending order of frequency, include anal melanomas, carcinoids, gastrointestinal stromal tumors (GISTs) and other sarcomas, and retrorectal tumors. Owing to the rarity of these tumors, exact incidences are difficult to determine. The incidence of anorectal melanoma is estimated at 1.7 cases per 100,000 population per year based on a review of cancer registries in the United States.1 There are approximately five new cases of carcinoids diagnosed per year for every 100,000 individuals in the United States. Twenty-five percent of these occur in the lower GI tract (5% in the appendix, 5% to 7% in the colon, and 14% in the rectum), for an estimated incidence of 1.25 per 100,000 per year.2 The overall incidence of GISTs is estimated at 1 to 2 per 100,000, with only about 5% in the lower GI tract.3 The incidence of colonic sarcomas has been reported at 0.04 per 100,000 per year, with appendiceal and rectal sarcomas also being incidentally reported.4 Retrorectal tumors are so rare that an overall incidence has not been determined; however, it is reported that between one and six patients are diagnosed annually at major referral centers.5,6 Though all of these lower GI tract tumors are rare, a thorough understanding of their management, as well as a high clinical suspicion for the diagnoses in the correct clinical setting, is essential for the surgical oncologist. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/03/28 UR - accesssurgery.mhmedical.com/content.aspx?aid=1145763126 ER -