ICD-10 Code C09.8 – Malignant neoplasm of overlapping sites of tonsil (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C09.8 – Malignant neoplasm of overlapping sites of tonsil
What it is
This code identifies a malignant tumor involving overlapping sites of the tonsil, meaning the cancer spans more than one tonsillar subsite. Use it when the documentation states overlapping involvement rather than a single, specific tonsil location.
Clinical signs
Clinical features vary; refer to documentation. Patients may have a visible tonsillar mass, persistent sore throat, dysphagia, referred ear pain, or cervical lymphadenopathy, but confirm the documented diagnosis before coding.
When to use this code
Use C09.8 when the provider documents primary malignant neoplasm of overlapping tonsillar sites, or when pathology and clinical notes identify tonsillar cancer crossing site boundaries. Code it for encounters focused on diagnosis, staging, or management of that confirmed malignancy.
Do not use for
Do not use this code for benign tonsillar lesions, dysplasia, or cancers limited to a single tonsil site when a more specific code is documented. Check documentation if the primary site is unclear.
Coding tip
Verify the exact anatomic wording in the pathology or oncology note; overlapping-site coding depends on documented site extent, not assumption.