C31.1 (Malignant neoplasm of ethmoidal sinus) compared with D38.5 (Neoplasm of uncertain behavior of other respiratory organs), from the official CMS tabular data. C31.1 and D38.5 name the same anatomical site (ethmoid) with a different neoplasm behavior.
Same anatomical site, different neoplasm behavior.
Same site — uncertain behavior (ethmoid)
The behavior documented for the site — malignant primary, secondary, carcinoma in situ, benign, uncertain or unspecified — decides which column of the neoplasm table, and therefore which code, applies.
Source: CMS Table of Neoplasms
Same site, different neoplasm behavior. C31.1 and D38.5 name the same anatomical site (ethmoid) with a different neoplasm behavior.
From the CMS Table of Neoplasms: the behavior documented for that site — malignant primary, secondary, carcinoma in situ, benign, uncertain or unspecified — decides which column, and therefore which code, applies.
| C31.1Malignant neoplasm of ethmoidal sinus | D38.5Neoplasm of uncertain behavior of other respiratory organs | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | C00-D49 — Neoplasms (C00-D49) | C00-D49 — Neoplasms (C00-D49) |
| Definition | Malignant neoplasm of ethmoidal sinus is a billable ICD-10-CM diagnosis code (C31.1). | Neoplasm of uncertain behavior of other respiratory organs is a billable ICD-10-CM diagnosis code (D38.5). |
| Includes | malignant neoplasm of middle ear | Neoplasm of uncertain behavior of accessory sinuses Neoplasm of uncertain behavior of cartilage of nose Neoplasm of uncertain behavior of middle ear Neoplasm of uncertain behavior of nasal cavities |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources