C26.9 vs C78.89

C26.9 (Malignant neoplasm of ill-defined sites within the digestive system) compared with C78.89 (Secondary malignant neoplasm of other digestive organs), from the official CMS tabular data. C26.9 and C78.89 name the same anatomical site (digestive organs) with a different neoplasm behavior.

Relationship

Informational

Neoplasm table relationship

C78.89

Secondary malignant neoplasm of other digestive organs

↔

C26.9

Malignant neoplasm of ill-defined sites within the digestive system

Same anatomical site, different neoplasm behavior.

Same site — primary malignancy (digestive organs)

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. C78.89 and C26.9 name the same anatomical site (digestive organs) 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	C78.89Secondary malignant neoplasm of other digestive organs
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).	Secondary malignant neoplasm of other digestive organs is a billable ICD-10-CM diagnosis code (C78.89).
Includes	Malignant neoplasm of alimentary canal or tract NOS Malignant neoplasm of gastrointestinal tract NOS	—

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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