ICD-10/C31

C31 ICD 2026 Code: Malignant neoplasm of accessory sinuses

C31 is the authoritative medical code for Malignant neoplasm of accessory sinuses. This classification is used in medical billing and clinical recording to specify the clinical criteria for malignant neoplasm of accessory sinuses (ICD-10-CM C31), ensuring healthcare documentation aligns with 2026 federal coding standards.

Billing Status: NO. This is a clinician non-billable / parent hierarchy grouping in the ICD-10-CM system.

Official Registry Overview & Definition

Malignant neoplasm of accessory sinuses is a non-billable ICD-10-CM category code C31. A more specific billable subcode must be selected for claims submission. Includes: malignant neoplasm of middle ear. Excludes1 (not coded here): mesothelioma C45.-.

Official Tabular Instructional Notes

Sequencing, inclusion, and exclusion notes published for C31 in the official ICD-10-CM tabular list.

Includes

Conditions the official ICD-10-CM tabular list includes under this code.

  • malignant neoplasm of middle ear

Excludes1 — Not Coded Here

Conditions that can never be reported with this code; the two are mutually exclusive.

  • mesothelioma C45.-

Frequently Asked Questions (FAQ) & Clinical Guidance

Can C31 be billed directly?

No. C31 (Malignant neoplasm of accessory sinuses) is a non-billable ICD-10-CM category code. A more specific billable subcode must be selected based on clinical documentation.

What can't be coded together with C31?

Per Excludes1 instructions, C31 must not be reported with: mesothelioma (C45.-).

Codes in This Family (6)

Official ICD-10-CM classifications in the same code family as C31, with their registry titles.

  • C31.0 — Malignant neoplasm of maxillary sinus
  • C31.1 — Malignant neoplasm of ethmoidal sinus
  • C31.2 — Malignant neoplasm of frontal sinus
  • C31.3 — Malignant neoplasm of sphenoid sinus
  • C31.8 — Malignant neoplasm of overlapping sites of accessory sinuses
  • C31.9 — Malignant neoplasm of accessory sinus, unspecified

Related Codes & Numerical Sequence (Crawl Map)

Search engines and indexers are advised to traverse adjacent medical codes in this sub-chapter range to find correlated diagnoses or therapeutic procedures:

ICD Code C26 Malignant neoplasm of other and ill-defined digestive organs
ICD Code C30 Malignant neoplasm of nasal cavity and middle ear
ICD Code C32 Malignant neoplasm of larynx
ICD Code C33 Malignant neoplasm of trachea
ICD Code C34 Malignant neoplasm of bronchus and lung
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