2025 Volume 78 Issue 10 Pages 373-385
Anal canal cancer is an uncommon tumor worldwide, and its incidence rate is also low in Japan. The histological type of anal canal cancer is predominantly squamous cell carcinoma in Western countries, whereas in Japan, most cases are adenocarcinomas. Regarding HPV infection in anal canal squamous cell carcinoma, the HPV positivity rate is also very high in Japan, similar to Western countries, with HPV-16 being the most common genotype. Additionally, the classifications and guidelines for anal canal cancer vary depending on the site of origin and histological type. In Japan, for rectal-type adenocarcinomas, the Japanese Classification of Colorectal, Appendiceal, and Anal Carcinoma 9th edition is used, while for squamous cell carcinomas, adenocarcinoma of anal glands and adenocarcinoma associated with anorectal fistula, the UICC TNM classification 8th edition is used. Regarding treatment, surgical therapy is the primary treatment for adenocarcinoma cases, while chemoradiotherapy is the primary treatment for squamous cell carcinoma cases. However, there are few reports on anal canal cancer both in Japan and internationally. Therefore, it is important to accumulate more cases and establish appropriate classifications and treatment guidelines in the future.
