Summary

• In 1976, WHO published the first edition of the International Classification of Diseases for Oncology (ICD-O), which had a topography section based on the malignant neoplasm rubrics of ICD and a morphology section that was a one-digit expansion of the MOTNAC morphology.
• The Third Edition of ICD-O was published in 2000 and is intended to be used for cancer cases diagnosed on January 1, 2001 and forward. The ICD-O continues to be revised in order to keep up with medical advances.
• ICD-O is a dual classification with coding systems for both topography and morphology.
• In ICD-O, the topography code describes the site of origin of the neoplasm, and the morphology code describes the cell type of the tumor and its biologic activity.
• ICD-O consists of five main sections:
  • Instructions for Use
  • Topography-Numerical List
  • Morphology-Numerical List
  • Alphabetic Index
  • Differences in Morphology Codes between ICD-O-3 and ICD-O-2
• The topography section has been adapted from the malignant neoplasm section of Chapter II of ICD.
• The terms are listed under both the noun and the adjective in the alphabetic index.
• In the alphabetic index, any word that appears as part of three or more terms is in bold type.
• The code for a term followed by "NOS" should be used when:
  • a topographic or morphologic term is not modified;
  • a topographic or morphologic term has an adjective that does not appear elsewhere
  • a term is used in a general sense
• SEER provides guidelines for coding primary site in an abstract in the SEER Program Coding and Staging Manual.
• The SEER Coding and Staging Manual, Appendix C contains instruction on coding primary site for some sites.
• Refer to the Heme manual and the Heme DB for primary site coding instructions for hematopoietic and lymphoid neoplasm.
• While not the principal reference for coding primary site, the Solid Tumor rules do include primary site coding instructions for some sites.
• SEER*Educate is a free, comprehensive training platform cancer registry professionals and students can use to improve technical skills through applied testing on the latest coding guidelines and concepts.

Updated: December 13, 2023