ICD-10 Code C00.4 – Malignant neoplasm of lower lip, inner aspect (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C00.4 – Malignant neoplasm of lower lip, inner aspect
What it is
C00.4 identifies a malignant tumor arising on the inner aspect of the lower lip. Use it when documentation specifies this exact site, not the outer lip or other oral locations.
Clinical signs
Clinical features may include a persistent ulcer, indurated lesion, bleeding, pain, or a nonhealing mass on the inner lower lip. Clinical features vary; refer to documentation.
When to use this code
Use C00.4 when the provider documents primary cancer of the lower lip’s inner surface, including pathology or operative notes that localize the tumor there. If the record only says “lip cancer” or another lip site, check documentation before assigning this code.
Do not use for
Do not use it for malignant neoplasms of the outer lower lip, upper lip, or adjacent oral cavity sites. If the anatomic site is unclear, check documentation.
Coding tip
Confirm the exact lip subsite in the pathology, exam, or operative report before coding.