2026 ICD-10-CM Diagnosis Code C31.8Malignant neoplasm of overlapping sites of accessory sinuses
ICD-10-CM Codes›C00–D49›C30-C39›C31
- Billable — Valid for Submission
- Chronic Condition
C31.8 is a billable ICD-10-CM diagnosis code for malignant neoplasm of overlapping sites of accessory sinuses. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 146 through 148. Coders also document this condition as adenocarcinoma of accessory sinus. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Head and neck cancers - all other types.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Adenocarcinoma of accessory sinus
- Malignant melanoma of accessory sinus
- Overlapping malignant neoplasm of accessory sinuses
- Primary adenocarcinoma of accessory sinus
- Primary adenocarcinoma of overlapping sites of accessory sinuses
- Primary malignant melanoma of overlapping sites of accessory sinuses
- Primary squamous cell carcinoma of accessory sinus
- Primary squamous cell carcinoma of overlapping sites of accessory sinuses
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Table of NeoplasmsClinical
Anatomical sites in the Table of Neoplasms that reference this code family.
| Site | Malig. Primary | Malig. Secondary | Ca in situ | Benign | Uncertain | Unspec. |
|---|---|---|---|---|---|---|
| ear (external) [See Also: Neoplasm, skin, ear] › overlapping lesion with accessory sinuses | C31.8 | – | – | – | – | – |
| sinus (accessory) › overlapping lesion | C31.8 | – | – | – | – | – |
Patient EducationClinical
Nasal Cancer
Your paranasal sinuses are small hollow spaces around the nose. They are lined with cells that make mucus, which keeps your nose from drying out. The nasal cavity is the passageway just behind your nose. Air passes through it on the way to your throat as you breathe.
Read the full article at MedlinePlus
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Convert C31.8 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About C31.8Overview
Is C31.8 (Malignant neoplasm of accessory sinuses) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report malignant neoplasm of overlapping sites of accessory sinuses on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does C31.8 group to?
When malignant neoplasm of overlapping sites of accessory sinuses is the principal diagnosis on an inpatient stay, it groups to MS-DRG 146, 147, 148, with relative weights from 0.7971 to 2.1174 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of C31.8?
Under the General Equivalence Mappings, malignant neoplasm of overlapping sites of accessory sinuses converts to ICD-9-CM 160.8 (mal neo access sinus NEC). The mapping is a direct match.
Footnotes
[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:
- The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
- The condition places limitations on self-care, independent living, and social interactions.
