ICD-10 Code C31.3 – Malignant neoplasm of sphenoid sinus (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C31.3 – Malignant neoplasm of sphenoid sinus
What it is
C31.3 identifies a malignant tumor arising in the sphenoid sinus, one of the paranasal sinuses located deep behind the nose. Use it when documentation specifies cancer of the sphenoid sinus.
Clinical signs
Clinical features vary; refer to documentation. Reported findings may include nasal obstruction, headache, facial pain, or symptoms from nearby structure involvement, but you should code only what is documented.
When to use this code
Use C31.3 when the provider documents primary malignant neoplasm of the sphenoid sinus, including confirmed cancer in that site. It is also appropriate when the record clearly identifies the sphenoid sinus as the primary location of the malignancy. Check documentation if the site is described only as sinonasal or paranasal.
Do not use for
Do not use this code for benign sinus tumors, inflammation, or unspecified nasal cavity cancers. If the cancer site is not clearly the sphenoid sinus, check documentation before coding.
Coding tip
Confirm the exact anatomic site in the pathology or provider note before assigning C31.3.