In coding for a patient with known metastatic disease, which scenario requires the use of code C80.0?

The use of code C80.0, which designates "Malignant neoplasm without specification of site," is specifically applicable when the primary site of the metastatic disease is not identified. In cases of metastasis, it is crucial to code accurately based on the details available for the patient. If the origin of the cancer cannot be determined, coding with C80.0 is necessary to reflect that the cancer is metastatic without a specified primary location. This ensures that the medical record accurately represents the patient's diagnosis and allows for appropriate treatment and management of their condition.

The other scenarios listed do not warrant the use of code C80.0. For instance, treatment exclusively for the primary site would require codes that specifically identify that primary site, while a resolved malignancy would not be coded as active cancer at all. Additionally, seeking symptom relief without documenting the primary neoplasm also would not necessitate using C80.0, since there would typically be other codes available to reflect the current medical situation.