C18.1 (Malignant neoplasm of appendix) compared with D49.0 (Neoplasm of unspecified behavior of digestive system), from the official CMS tabular data. C18.1 and D49.0 name the same anatomical site (appendix) with a different neoplasm behavior.
Same anatomical site, different neoplasm behavior.
Same site — unspecified behavior (appendix)
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. C18.1 and D49.0 name the same anatomical site (appendix) 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.
| C18.1Malignant neoplasm of appendix | D49.0Neoplasm of unspecified behavior of digestive system | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | C00-D49 — Neoplasms (C00-D49) | C00-D49 — Neoplasms (C00-D49) |
| Definition | Malignant neoplasm of appendix is a billable ICD-10-CM diagnosis code (C18.1). | Neoplasm of unspecified behavior of digestive system is a billable ICD-10-CM diagnosis code (D49.0). |
| Includes | — | 'growth' NOS neoplasm NOS new growth NOS tumor NOS |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources