minimal Common Oncology Data Elements (mCODE) Implementation Guide
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minimal Common Oncology Data Elements (mCODE) Implementation Guide, published by HL7 International / Clinical Interoperability Council. This guide is not an authorized publication; it is the continuous build for version 4.0.0-ballot built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of and changes regularly. See the Directory of published versions


This implementation guide draws on a number of formal terminologies (code systems). Several guiding principles were applied in selecting terminologies for mCODE:

  1. Fit for purpose
  2. Conformance with US Core and FHIR
  3. Commonly used in real world practice

The following table presents the external code systems (and naming conventions) adopted in mCODE, and their primary purpose:

Code System Domain FHIR IG Publishing support? HL7 Canonical
CPT Procedure codes No
HGNC Gene identification No
HGVS Sequence variant nomenclature Yes
HTA Various HL7 V2 and FHIR-specific codes Yes
ICD-O-3 Cancer morphology and topology codes No
ICD-10-CM Diagnosis codes Yes
ICD-10-PCS Procedure codes No
LOINC Observation and laboratory codes, answer codes Yes
NCBI GTR Genomic test codes No
NCBI ClinVar Genomic variations No
NCIT Cancer terminology No
RxNorm Medication codes Yes
Sequence Ontology DNA change types No
SNOMED CT Disorders, body structures, findings, qualifiers Yes
UCUM Units of measure Yes


  • CPT - Current Procedural Terminology (American Medical Association)
  • HGNC - Human Genome Organisation (HUGO) Gene Nomenclature Committee
  • HGVS - Human Genome Variation Society
  • HTA - HL7 Terminology Authority
  • ICD - International Classification of Diseases (World Health Organization)
    • ICD-O-3 - Oncology, 3rd revision
    • ICD-10-CM - Clinical Modification, 10th revision
    • ICD-10-PCS - Procedure Coding System, 10th revision
  • LOINC - Logical Observation Identifiers Names and Codes
  • NCBI - National Center for Biotechnology Information (National Institutes of Health) (US)
    • NCBI GTR - Genomic Testing Registry
    • NCBI ClinVar - Not an acronym
  • NCIT - National Cancer Institute (NCI) Thesaurus
  • RxNorm - From National Library of Medicine (US)
  • SNOMED CT - Systematized Nomenclature of Medicine Clinical Terms
  • UCUM - Unified Code for Units of Measure
  • UMLS - Unified Medical Language System Metathesaurus

Local Code Systems

Local code systems SnomedRequestedCS are provided for terms submitted but not yet published and/or approved by SNOMED. It is expected that the local codes will be replaced with approved LOINC and SNOMED terms in a future technical correction to the STU 2 IG. Where codes have already been assigned by SNOMED, but not yet published, those codes are used as local codes to reduce future changes. In other cases, the submission numbers are used as the local codes.