Rare cancers of gastrointestinal system with an accent on anal cancer

There is no universally adopted definition for rare cancers. The National Cancer Institute definition is fewer than 15 cases per 100,000 people per year. More recently, a consortium from the European Union (RARECARE) defined rare cancers as those with fewer than 6 cases per 100,000 people per year, which is the definition we use in this report. Historically, cancers have been categorized by the location in the body (anatomic site) and type of tissue (histology) from which they originate. Today, genetic information is increasingly used to group cancers according to a molecular subtype resulting in the subdivision of some more common cancers into a collection of rarer cancers. However, given the limited data on molecular subtypes available from cancer registries, the cancers described herein are primarily defined by site of origin like hepatocellular carcinoma,cholangiocelullar carcinoma, gastrointestinal stromal tumor and anal cancer. (author)