C15 refers to a specific classification in the C15 series of the International Classification of Diseases (ICD), which is used to categorize various health conditions. This classification helps healthcare professionals identify and code diseases for diagnosis, treatment, and research purposes. In the context of C15, it primarily pertains to cancers of the esophagus. This includes various types of esophageal cancer, which can affect the lining of the esophagus and may require different treatment approaches based on the specific type and stage of the disease.