Carcinoma in situ of floor of mouth

This code signifies the presence of abnormal, non-invasive epithelial cells confined to the mucosal surface of the floor of the mouth, without evidence of invasion into deeper tissues. It represents a pre-malignant condition, also known as severe dysplasia or intraepithelial neoplasia, which has the potential to progress to invasive squamous cell carcinoma if left untreated.

Apply this code when documentation clearly states "carcinoma in situ," "severe dysplasia," or "intraepithelial neoplasia" specifically located on the floor of the mouth. This diagnosis is typically confirmed by biopsy and subsequent histopathological examination. It is appropriate for initial diagnosis and follow-up encounters where the in situ nature of the lesion is confirmed.

• Ensure the documentation explicitly specifies "in situ" and the anatomical site as the "floor of mouth" to differentiate from invasive carcinoma or other oral cavity sites.
• Do not use this code for invasive squamous cell carcinoma of the floor of mouth; instead, refer to codes in the C04.- series.
• Consider any associated risk factors (e.g., tobacco, alcohol use) for additional coding, if documented.