C26.9 vs D01.9

C26.9 (Malignant neoplasm of ill-defined sites within the digestive system) compared with D01.9 (Carcinoma in situ of digestive organ, unspecified), from the official CMS tabular data. C26.9 and D01.9 name the same anatomical site (alimentary canal or tract) with a different neoplasm behavior.

Relationship

Informational

Neoplasm table relationship

C26.9

Malignant neoplasm of ill-defined sites within the digestive system

↔

D01.9

Carcinoma in situ of digestive organ, unspecified

Same anatomical site, different neoplasm behavior.

Same site — carcinoma in situ (alimentary canal or tract)

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

Can these codes be reported together?

Same site, different neoplasm behavior. C26.9 and D01.9 name the same anatomical site (alimentary canal or tract) 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.

Side by side

	C26.9Malignant neoplasm of ill-defined sites within the digestive system	D01.9Carcinoma in situ of digestive organ, unspecified
Billing status	Billable	Billable
Classification	C00-D49 — Neoplasms	C00-D49 — Neoplasms
Definition	Malignant neoplasm of ill-defined sites within the digestive system is a billable ICD-10-CM diagnosis code (C26.9).	Carcinoma in situ of digestive organ, unspecified is a billable ICD-10-CM diagnosis code (D01.9).
Includes	Malignant neoplasm of alimentary canal or tract NOS Malignant neoplasm of gastrointestinal tract NOS	Bowen's disease erythroplasia grade III intraepithelial neoplasia Queyrat's erythroplasia

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Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources