Neoplasm of uncertain behavior of appendix

This code signifies a tumor of the appendix where the pathologist cannot definitively classify it as benign or malignant based on microscopic examination. It indicates an abnormal growth with features that are intermediate between clearly benign and clearly cancerous.

This code is appropriate when pathology reports describe an appendiceal neoplasm as "uncertain behavior," "borderline," or "low malignant potential." It should be used when there is insufficient evidence to assign a more specific benign or malignant code.

• Requires definitive pathology documentation of "uncertain behavior" for the appendix.
• Do not use if the pathology clearly states benign (e.g., adenoma) or malignant (e.g., adenocarcinoma).
• Always sequence as the primary diagnosis when it is the reason for the encounter or treatment.