2027 ICD-10-CM Diagnosis Code C31Malignant neoplasm of accessory sinuses

ICD-10-CM Codes›C00–D49›C30-C39›C31

ICD-10-CM C31
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

C31 is a non-billable ICD-10-CM category code for malignant neoplasm of accessory sinuses, so it cannot be submitted on claims. Use a more specific code from this category instead, such as C31.0, C31.1, C31.2, and C31.3.

Code Identity

ICD-10-CM Code
C31
Billable Status
No — Non-Billable Category
Code Describes
Malignant neoplasm of accessory sinuses
Short Description
Malignant neoplasm of accessory sinuses
Same as the full description in the CMS dataset.
Chapter
C30-C39
Malignant neoplasms of respiratory and intrathoracic organs

Code Classification

ChapterC00–D49Neoplasms
SectionC30-C39Malignant neoplasms of respiratory and intrathoracic organs
CategoryC31Malignant neoplasm of accessory sinuses
This CodeC31Malignant neoplasm of accessory sinuses

Specific Coding for Malignant neoplasm of accessory sinusesOverview

Non-specific codes like C31 require more characters. Use one of these billable codes instead:

  • Use C31.0 for Malignant neoplasm of maxillary sinus

  • Use C31.1 for Malignant neoplasm of ethmoidal sinus

  • Use C31.2 for Malignant neoplasm of frontal sinus

  • Use C31.3 for Malignant neoplasm of sphenoid sinus

  • Use C31.8 for Malignant neoplasm of overlapping sites of accessory sinuses

  • Use C31.9 for Malignant neoplasm of accessory sinus, unspecified

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to C31: its own notes plus those printed at block C30-C39 and Chapter 2. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Block C30-C39 Malignant neoplasms of respiratory and intrathoracic organs applies to 40 codes
  • malignant neoplasm of middle ear

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From Block C30-C39 Malignant neoplasms of respiratory and intrathoracic organs applies to 40 codes

Notes

General instructions on how these codes are used.

From Chapter 2 (C00-D49) Neoplasms applies to 1,730 codes
  • Functional activity
  • All neoplasms are classified in this chapter, whether they are functionally active or not. An additional code from Chapter 4 may be used, to identify functional activity associated with any neoplasm.
  • Morphology [Histology]
  • Chapter 2 classifies neoplasms primarily by site (topography), with broad groupings for behavior, malignant, in situ, benign, etc. The Table of Neoplasms should be used to identify the correct topography code. In a few cases, such as for malignant melanoma and certain neuroendocrine tumors, the morphology (histologic type) is included in the category and codes.
  • Primary malignant neoplasms overlapping site boundaries
  • A primary malignant neoplasm that overlaps two or more contiguous (next to each other) sites should be classified to the subcategory/code .8 ('overlapping lesion'), unless the combination is specifically indexed elsewhere. For multiple neoplasms of the same site that are not contiguous, such as tumors in different quadrants of the same breast, codes for each site should be assigned.
  • Malignant neoplasm of ectopic tissue
  • Malignant neoplasms of ectopic tissue are to be coded to the site mentioned, e.g., ectopic pancreatic malignant neoplasms are coded to pancreas, unspecified (C25.9).

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name C31, its category, or a range that includes it.

Applicable To 2

These notes mention C31.

  • Z80.2 Family history of malignant neoplasm of other respiratory and intrathoracic organs
    Conditions classifiable to C30-C32, C37-C39 names C30-C32, which includes this code
  • Z85.22 Personal history of malignant neoplasm of nasal cavities, middle ear, and accessory sinuses
    Conditions classifiable to C30-C31 names C30-C31, which includes this code

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

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About C31Overview

What is the ICD-10 code for malignant neoplasm of accessory sinuses?

C31 is the ICD-10-CM category for malignant neoplasm of accessory sinuses, but it is a non-billable header: claims need a more specific code from this category, listed on this page.

Is C31 (Malignant neoplasm of accessory sinuses) a billable code?

No. This is a category header that groups the codes for malignant neoplasm of accessory sinuses, and headers cannot be submitted on claims. Claims for malignant neoplasm of accessory sinuses need a more specific code from this category, such as C31.0, C31.1, and C31.2.

Can C31 be reported with a code from C45?

Not as a rule. The Excludes1 note at block C30-C39, which applies to C31, lists "mesothelioma (C45.-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).