Neoplasm of uncertain behavior of peritoneum

This code signifies a tumor originating in the peritoneum (the membrane lining the abdominal cavity and covering its organs) that pathologists cannot definitively classify as benign or malignant based on current diagnostic criteria. It indicates an abnormal growth with some features suggestive of malignancy but lacking sufficient evidence for a definitive cancer diagnosis.

Apply this code when pathology reports describe a peritoneal neoplasm as "uncertain," "borderline," or "of uncertain malignant potential." This is appropriate when the tumor exhibits atypical cellular features but does not meet the full criteria for malignancy, and further observation or investigation is required.

• Ensure the pathology report explicitly states "uncertain behavior" or similar terminology for the peritoneal lesion.
• Do not use this code if the tumor is definitively diagnosed as benign (e.g., peritoneal cyst) or malignant (e.g., peritoneal carcinomatosis).
• Review the entire pathology report for any additional information that might clarify the tumor's behavior, such as mitotic activity or invasion.