C04.9 vs D37.09

C04.9 (Malignant neoplasm of floor of mouth, unspecified) compared with D37.09 (Neoplasm of uncertain behavior of other specified sites of the oral cavity), from the official CMS tabular data. C04.9 and D37.09 name the same anatomical site (mouth) with a different neoplasm behavior. MedCoder-derived

Relationship

Informational

Neoplasm table relationship

C04.9

Malignant neoplasm of floor of mouth, unspecified

↔

D37.09

Neoplasm of uncertain behavior of other specified sites of the oral cavity

Same anatomical site, different neoplasm behavior.

Same site — uncertain behavior (mouth)

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. C04.9 and D37.09 name the same anatomical site (mouth) 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

	C04.9Malignant neoplasm of floor of mouth, unspecified	D37.09Neoplasm of uncertain behavior of other specified sites of the oral cavity
Billing status	Billable	Billable
Classification	C00-D49 — Neoplasms	C00-D49 — Neoplasms
Definition	Malignant neoplasm of floor of mouth, unspecified is a billable ICD-10-CM diagnosis code (C04.9).	Neoplasm of uncertain behavior of other specified sites of the oral cavity is a billable ICD-10-CM diagnosis code (D37.09).
Use additional code	code to identify: alcohol abuse and dependence (F10.-) history of tobacco dependence (Z87.891)	—

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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