Neoplasm of uncertain behavior of retroperitoneum and peritoneum

This code signifies the presence of an abnormal growth in the retroperitoneal space or the peritoneum that cannot definitively be classified as benign or malignant based on current pathological examination. These neoplasms exhibit features that are intermediate between benign and malignant, requiring further investigation or monitoring.

Assign this code when pathology reports describe a tumor of the retroperitoneum or peritoneum as "uncertain behavior," "borderline malignancy," or "of undetermined malignant potential." This is appropriate when the pathologist cannot provide a definitive benign or malignant diagnosis after microscopic examination.

• Ensure the documentation explicitly states "uncertain behavior" or similar terminology for a retroperitoneal or peritoneal neoplasm.
• Do not use this code if the pathology definitively identifies the neoplasm as benign (e.g., lipoma, fibroma) or malignant (e.g., sarcoma, carcinoma).
• Review the entire pathology report; sometimes, a definitive diagnosis is provided later in the report or in an addendum.