ICD-10/C31.1

C31.1 ICD 2026 Code: Malignant neoplasm of ethmoidal sinus

C31.1 is the authoritative medical code for Malignant neoplasm of ethmoidal sinus. This classification is used in medical billing and clinical recording to specify the clinical criteria for malignant neoplasm of ethmoidal sinus (ICD-10-CM C31.1), ensuring healthcare documentation aligns with 2026 federal coding standards.

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Official Registry Overview & Definition

Malignant neoplasm of ethmoidal sinus is a billable ICD-10-CM diagnosis code C31.1. Includes: malignant neoplasm of middle ear. Excludes1 (not coded here): mesothelioma C45.-.

Official Tabular Instructional Notes

Sequencing, inclusion, and exclusion notes published for C31.1 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

What can't be coded together with C31.1?

Per official ICD-10-CM Excludes1 instructions, C31.1 must not be reported together with: mesothelioma (C45.-).

Nearest Codes in This Family

Official ICD-10-CM classifications closest to C31.1 in its code family, with their registry titles.

  • C31 — Malignant neoplasm of accessory sinuses
  • C31.0 — Malignant neoplasm of maxillary 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

Neoplasm Table Sites (2)

Anatomical sites from the official ICD-10-CM Table of Neoplasms that map to this code, with the matching behavior column.

  • Neoplasm, neoplastic, ethmoid (sinus) — Malignant, Primary
  • Neoplasm, neoplastic, sinus (accessory), ethmoidal — Malignant, Primary