Other malignant neoplasm without specification of site

This code signifies a malignant tumor where the primary site is unknown or unspecified in the medical record. It indicates a confirmed diagnosis of cancer, but further diagnostic workup or documentation is lacking regarding its origin. This is often used for metastatic disease where the primary tumor has not been identified.

Use this code when the pathology report confirms malignancy, but the physician's documentation explicitly states "malignant neoplasm, site unknown" or "carcinoma of unknown primary." It is appropriate when extensive diagnostic efforts have failed to pinpoint the primary site, or when the patient presents with widespread metastatic disease without an identifiable primary.

• Avoid using this code if any primary site, even a probable one, is documented; instead, query the physician for clarification.
• This code should be a last resort when all efforts to identify a specific primary site have been exhausted.
• Always sequence this code after any codes for known metastatic sites, if applicable.