If a patient is admitted for a primary neoplasm with metastasis and treatment is directed toward the secondary site only, what is the principal diagnosis?

The principal diagnosis is classified as the secondary neoplasm when treatment is specifically directed toward the metastatic or secondary site. In ICD-10-CM coding, the focus is on the site of the active disease requiring treatment. In cases where a primary neoplasm presents with metastases, and the treatment is solely aimed at the secondary site, coding guidelines dictate that the secondary neoplasm should be prioritized.

This approach is consistent with the guideline that the principal diagnosis must reflect the condition for which the patient is primarily receiving care during an admission. Therefore, even though the primary neoplasm is clinically significant, the emphasis on treating the secondary site means that it should be coded as the principal diagnosis to accurately represent the primary focus of the medical treatment.

This coding clarity helps in statistical reporting and resource allocation, ensuring that the secondary site, which is currently active and being treated, is properly recorded for healthcare analytics and reimbursement purposes.