California Cancer Reporting System Standards Volume I: Abstracting and Coding Procedures for Hospitals
Because topographic codes do not distinguish between the right and left side of a paired site - such as the lung - the location (laterality) of a primary tumor must be recorded. The main purpose is to identify the origin of the tumor.
See Section V.2.1 Coding (Laterality)
See Section V.2.2 Principal Paired Sites
See Section V.2.3 Site Coding Restriction