This is the CodeSystem that contains all the codes in US Pathology Code System (http://hl7.org/fhir/us/cancer-reporting/CodeSystem/us-pathology-codesystem) and US Pathology Code System (http://hl7.org/fhir/us/cancer-reporting/CodeSystem/us-pathology-codesystem). E.g. what you have to deal with if you get resources containing codes in either of them