ICD-O-3 Primary Site

Proper coding of primary site is critical to the quality of a cancer abstract. The primary site code impacts the appropriate histology code, staging options, and treatment codes in an abstract. Furthermore, Primary Site is a key variable used to describe the burden of cancer in the general population.

In the ICD-O Coding Primary Site module, you will gain an understanding of the primary site coding guidelines covered in ICD-O, and specifically how to use them in a cancer registry abstract.

In this module you will learn to

  • Describe the historical background of ICD-O.
  • Briefly explain the differences between ICD-O and ICD-10.
  • Describe the structure and format of ICD-O.
  • Code the site of a neoplasm based on the information from the medical record, using ICD-O as a reference tool.

This Module will take approximately 30-60 minutes to complete.

Updated: December 13, 2023


Suggested Citation

SEER Training Modules: ICD-O-3 Primary Site. U.S. National Institutes of Health, National Cancer Institute. Cited 20 December 2025. Available from: https://training.seer.cancer.gov.