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C39.9 vs D49.1

C39.9 (Malignant neoplasm of lower respiratory tract, part unspecified) compared with D49.1 (Neoplasm of unspecified behavior of respiratory system), from the official CMS tabular data. C39.9 and D49.1 name the same anatomical site (respiratory) with a different neoplasm behavior. MedCoder-derived

Relationship

Informational

Neoplasm table relationship

D49.1
Neoplasm of unspecified behavior of respiratory system
↔
C39.9
Malignant neoplasm of lower respiratory tract, part unspecified

Same anatomical site, different neoplasm behavior.

Same site — primary malignancy (respiratory)

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. D49.1 and C39.9 name the same anatomical site (respiratory) 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

C39.9Malignant neoplasm of lower respiratory tract, part unspecifiedD49.1Neoplasm of unspecified behavior of respiratory system
Billing statusBillableBillable
ClassificationC00-D49 — NeoplasmsC00-D49 — Neoplasms
DefinitionMalignant neoplasm of lower respiratory tract, part unspecified is a billable ICD-10-CM diagnosis code (C39.9).Neoplasm of unspecified behavior of respiratory system is a billable ICD-10-CM diagnosis code (D49.1).
Includes
malignant neoplasm of middle ear
Malignant neoplasm of respiratory tract NOS
'growth' NOS
neoplasm NOS
new growth NOS
tumor NOS
Use additional code
code to identify:
exposure to environmental tobacco smoke (Z77.22)
exposure to tobacco smoke in the perinatal period (P96.81)
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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