What is a bezoar?

A bezoar is specifically a mass that forms in the gastrointestinal (GI) system, typically as a result of the accumulation of indigestible materials, such as food, hair, or plant fibers. This mass can lead to various complications, depending on its location and size, including obstruction or irritation of the gastrointestinal tract. Bezoars are most commonly associated with the stomach but can occur at any place in the digestive system.

The other options provided do not accurately define a bezoar. A tumor formed in the stomach refers more to neoplastic growths, while inflammation of the stomach lining is described by terms like gastritis. Chronic gastritis refers to a persistent inflammation of the gastric mucosa, which is fundamentally different from the composition and origin of a bezoar. Thus, the characterization of a bezoar as a mass trapped in the GI system is the most accurate among the choices given.