Neoplasm of uncertain behavior of skin

This code signifies a skin lesion or growth that has been biopsied or excised, but the pathologist cannot definitively classify it as benign or malignant. The cellular characteristics exhibit some atypical features, but not enough to confirm malignancy, nor are they clearly benign.

This code is appropriate when pathology reports describe a skin neoplasm as "atypical," "of uncertain malignant potential," or "indeterminate." It is used when the clinician suspects a neoplastic process, but the final pathology is inconclusive regarding its benign or malignant nature.

• Always await the final pathology report before assigning this code; clinical suspicion alone is insufficient.
• Carefully review "Excludes1" notes to avoid incorrect co-coding with neoplasms of the anus, genital skin, or vermilion border of the lip.
• If a subsequent biopsy or excision definitively classifies the lesion as benign or malignant, update the diagnosis accordingly.