ICD-10 Code C34.3 – Malignant neoplasm of lower lobe, bronchus or lung (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C34.3 – Malignant neoplasm of lower lobe, bronchus or lung
What it is
C34.3 identifies a malignant tumor arising in the lower lobe of the lung or its bronchus. Use it when the record clearly localizes the primary cancer to that anatomic site.
Clinical signs
Clinical features vary; refer to documentation. Common findings may include cough, hemoptysis, dyspnea, chest pain, or an imaging-detected lung mass, but the site must be confirmed in the chart.
When to use this code
Assign C34.3 when the provider documents primary lung cancer in the lower lobe or lower-lobe bronchus. Use it for pathology, imaging, or oncology notes that specify this location. If the site is described only as lung cancer without lobe detail, check documentation.
Do not use for
Do not use C34.3 for metastatic disease to the lung or for cancers in another lobe. If the note does not specify the lower lobe, do not guess.
Coding tip
Code the documented primary site exactly as stated, and query for laterality or lobe detail only when the record is unclear.