Is ICD-10-CM code C31 billable?

No, C31 (Malignant neoplasm of accessory sinuses) is a non-billable ICD-10-CM code. It must be coded to a more specific subcategory before it can be used for reimbursement.

What chapter does ICD-10-CM code C31 belong to?

C31 belongs to Chapter 2 of the ICD-10-CM tabular list: C00–D49 (Neoplasms).

C31Not billable, use a more specific code below

Malignant neoplasm of accessory sinuses

In Malignant neoplasms of respiratory and intrathoracic organs (C30-C39), chapter 2: Neoplasms

6 billable codes under C31: none are a CC or MCC; all map to HCC 21 (Lymphoma and Other Cancers).An HCC counts toward a Medicare Advantage patient's risk score.

Instructional notes

Also applies, from Malignant neoplasms of respiratory and intrathoracic organs (C30-C39)

These notes sit on C30-C39 and apply to every code under it, including C31.

Includes: conditions that are coded here

malignant neoplasm of middle ear

Excludes1: not coded here, use a different code

mesothelioma (C45.-)

Official coding guidelines

From the ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027 (CMS and NCHS). Links open the PDF at the right page.

Rules for coding benign and malignant neoplasms: using the Neoplasm Table, sequencing primary and secondary sites, treatment encounters, complications, and current cancer versus personal history.

Admission/Encounter for treatment of primary site (page 33)
Admission/Encounter for treatment of secondary site (page 33)
Coding and sequencing of complications (page 34)
Primary malignancy previously excised (page 34)
Admissions/Encounters involving antineoplastic chemotherapy, immunotherapy and radiation therapy (page 35)
Admission/encounter to determine extent of malignancy (page 36)
Symptoms, signs, and abnormal findings listed in Chapter 18 associated with neoplasms (page 36)
Admission/encounter for pain control/management (page 36)

Read Section I.C.2 (page 32), 12 more topics

All codes under C31

C31 can't be used on a claim. Pick a billable code below; grey headings group them.

C31 MS-DRGs

This code does not group to an MS-DRG as a principal diagnosis.

Other codes that refer to C31

Notes on these codes point to C31.

Z85.22 Includes: Conditions classifiable to C30-C31

About the condition

Plain-language background from MedlinePlus (National Library of Medicine), not coding guidance.

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.

Code history

Valid since FY2016, when ICD-10-CM took effect on October 1, 2015. No changes since.