C78.80 vs D37.9

C78.80 (Secondary malignant neoplasm of unspecified digestive organ) compared with D37.9 (Neoplasm of uncertain behavior of digestive organ, unspecified), from the official CMS tabular data. C78.80 and D37.9 name the same anatomical site (alimentary canal or tract) with a different neoplasm behavior. MedCoder-derived

Relationship

Informational

Neoplasm table relationship

C78.80

Secondary malignant neoplasm of unspecified digestive organ

↔

D37.9

Neoplasm of uncertain behavior of digestive organ, unspecified

Same anatomical site, different neoplasm behavior.

Same site — uncertain behavior (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. C78.80 and D37.9 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

	C78.80Secondary malignant neoplasm of unspecified digestive organ	D37.9Neoplasm of uncertain behavior of digestive organ, unspecified
Billing status	Billable	Billable
Classification	C00-D49 — Neoplasms (C00-D49)	C00-D49 — Neoplasms (C00-D49)
Definition	Secondary malignant neoplasm of unspecified digestive organ is a billable ICD-10-CM diagnosis code (C78.80).	Neoplasm of uncertain behavior of digestive organ, unspecified is a billable ICD-10-CM diagnosis code (D37.9).

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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