When coding for metastatic cancer, there are some terms that need to be understood to determine which cancer is primary and secondary for reporting purposes. The definition of cancer is abnormal cells –or- cells that do not die when they should –or- cells that change into something they should not be. Metastatic cancer is cancer of cells that have moved to a different part of the body.
“Primary” cancer is cancer comprised of cells from their original location in the body.
”Secondary” cancer is cancer of cells that have moved to a different location in the body than where they originally were located.
When assigning ICD 10 codes for reporting on the claim the cancer that is being treated at the encounter should be reported as the primary diagnosis, and the ICD10 code for cancer in the part of the body where the cancer originated should be reported as the secondary diagnosis.
For example, you are treating lung cancer at this encounter and this is the secondary cancer for a patient that had breast cancer initially. You would report lung cancer as the primary ICD10 code and the breast cancer as the secondary diagnosis code.