Malignant neoplasm of peritoneum, unspecified

This code signifies the presence of a cancerous tumor originating in the peritoneum, the membrane lining the abdominal cavity and covering abdominal organs. The specific primary site within the peritoneum is not documented or is unknown. This diagnosis indicates a malignant process affecting this serous membrane.

Utilize this code when documentation confirms a malignant neoplasm of the peritoneum, but the precise anatomical origin within the peritoneum is not specified by the clinician. This is often used when pathology reports confirm malignancy but do not pinpoint a more specific peritoneal site, or when the primary site is unknown after extensive workup.

• Only use this code when a more specific site within the peritoneum (e.g., parietal, visceral, omentum) cannot be identified.
• Distinguish from secondary malignant neoplasms of the peritoneum (metastasis to the peritoneum), which would be coded differently.
• Ensure documentation clearly states "malignant neoplasm" and "peritoneum" without further specification of the exact peritoneal location.