ICD-10 Code C04.1 – Malignant neoplasm of lateral floor of mouth (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C04.1 – Malignant neoplasm of lateral floor of mouth
What it is
C04.1 identifies a malignant tumor arising in the lateral portion of the floor of the mouth. Use this code when documentation specifies that exact oral cavity subsite.
Clinical signs
Clinical features vary; refer to documentation. Commonly recorded findings include an oral mucosal mass, ulceration, pain, bleeding, or difficulty with chewing, swallowing, or speech.
When to use this code
Use C04.1 when the provider documents primary cancer of the lateral floor of mouth, including pathology or operative reports that name this site. It also fits follow-up notes that restate the confirmed diagnosis. If the record only says “oral cavity cancer” or another subsite, check documentation before assigning C04.1.
Do not use for
Do not use this code for cancers of other oral cavity sites, such as tongue, gum, palate, or other floor-of-mouth subsites. If the lesion is described as metastatic or unspecified, check documentation.
Coding tip
Code the exact anatomic site documented; laterality matters less than the named floor-of-mouth subsite.