ICD-10 Code C09.1 – Malignant neoplasm of tonsillar pillar (anterior) (posterior) (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C09.1 – Malignant neoplasm of tonsillar pillar (anterior) (posterior)
What it is
C09.1 identifies a malignant tumor arising in the anterior or posterior tonsillar pillar. Use it when the record specifies cancer of this anatomic tonsillar pillar region.
Clinical signs
Clinical features vary; refer to documentation. Common findings may include a visible or palpable tonsillar pillar mass, throat pain, dysphagia, or referred ear pain, but the diagnosis must be documented.
When to use this code
Use C09.1 when the provider documents primary cancer of the tonsillar pillar, including anterior or posterior pillar involvement. It is also appropriate when pathology, imaging, or operative notes clearly localize the malignancy to this site. Check documentation if the tumor spans nearby or overlapping oropharyngeal structures.
Do not use for
Do not use this code for benign tonsillar lesions, inflammation, or unspecified tonsil cancer. If the site is described only as tonsil, oropharynx, or overlapping lesion, verify the exact anatomic location first.
Coding tip
Code from the most specific site stated in the record, and confirm whether the anterior or posterior tonsillar pillar is documented.