Carcinoma in situ of labial mucosa and vermilion border

This code signifies the presence of abnormal, non-invasive epithelial cells confined to the surface layer of the labial mucosa and the vermilion border of the lip. These cells exhibit malignant characteristics but have not penetrated the basement membrane. It represents a pre-invasive form of squamous cell carcinoma.

Use this code when documentation clearly indicates carcinoma in situ affecting the inner lining of the lip or the transitional zone between the skin and the red part of the lip. This diagnosis is typically confirmed by biopsy showing intraepithelial neoplasia without stromal invasion.

• Distinguish from invasive squamous cell carcinoma of the lip, which would be coded to the C00 series.
• Ensure the documentation specifies "in situ" or "intraepithelial" to support this diagnosis.
• Do not use for dysplasia or atypical hyperplasia without a definitive diagnosis of carcinoma in situ.