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C26.9 vs C78.80

C26.9 (Malignant neoplasm of ill-defined sites within the digestive system) compared with C78.80 (Secondary malignant neoplasm of unspecified digestive organ), from the official CMS tabular data. C26.9 and C78.80 name the same anatomical site (alimentary canal or tract) with a different neoplasm behavior. MedCoder-derived

Relationship

Informational

Neoplasm table relationship

C26.9
Malignant neoplasm of ill-defined sites within the digestive system
↔
C78.80
Secondary malignant neoplasm of unspecified digestive organ

Same anatomical site, different neoplasm behavior.

Same site — secondary malignancy (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 C78.80 name the same anatomical site (alimentary canal or tract) with a different neoplasm behavior.

From the CMS/CDC 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 systemC78.80Secondary malignant neoplasm of unspecified digestive organ
Billing statusBillableBillable
ClassificationC00-D49 — NeoplasmsC00-D49 — Neoplasms
DefinitionMalignant neoplasm of ill-defined sites within the digestive system is a billable ICD-10-CM diagnosis code (C26.9).Secondary malignant neoplasm of unspecified digestive organ is a billable ICD-10-CM diagnosis code (C78.80).
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