ICD-O consists of two main components: - Topography: This component uses codes to represent the anatomical site where the tumor originates. These codes are based on the ICD system and include a "C" prefix followed by a three-digit code and an optional fourth digit. - Morphology: This component classifies the histologic type of the tumor and its behavior (benign, malignant, in situ, etc.). The morphology codes consist of a four-digit number identifying the histologic type, followed by a one-digit behavior code.
