Disseminated malignant neoplasm without specification of site

This code signifies a widespread malignant tumor where the primary origin cannot be determined or is not documented. It indicates that cancer has spread throughout the body, but the initial site from which it arose is unknown. This diagnosis is typically made when metastatic disease is present, but a definitive primary tumor has not been identified after diagnostic workup.

Use this code when documentation explicitly states "disseminated malignant neoplasm without specification of site," "carcinoma of unknown primary with widespread metastases," or similar phrasing indicating extensive metastatic disease with an undetermined primary. It is appropriate when diagnostic efforts to locate the primary site have been exhausted or are ongoing, and the patient presents with widespread malignancy.

• Avoid using this code if a primary site is eventually identified, even if it was initially unknown.
• Do not use for localized malignancies of unknown primary; this code specifically implies dissemination.
• Always review the entire medical record for any clues to the primary site before assigning this code.