Lung Mass – Differential Diagnosis

History: 60 year old male with cough. 

Adenocarcinoma of the lung: Axial CT scan of the chest with contrast reveals a lung mass with spiculated borders in the left lower lobe of the lung abutting the left major fissure.

A lung mass is a focal opacity that measures greater than 3 cm. If it measures less than 3 cm and is the only lesion, it is classified as a solitary pulmonary nodule. Read this post for the differential diagnosis for a solitary pulmonary nodule.

The differential diagnosis for a lung mass is as follows:

1. Lung cancer – adenocarcinoma is the most common, and it commonly will have spiculated borders, a pleural tail, or thick walled cavitation. Read this post for a differential diagnosis for a cavitating lung mass.

2. Lung Metastases – most common in the lower lung zones due to hemondynamic factors, commonly multiple.

3. Mycobacterial, fungal pneumonia, or lung abscess

4. Pulmonary pseudotumor – loculated pleural fluid in a pulmonary fissure which is commonly lenticular in shape.

5. Round atelectasis – read this post regarding round atelectasis for a good case example.

Other less common entities on the differential for a lung mass include pulmonary AVM, hematoma, bronchogenic cyst, pulmonary sequestration, and hydatid cyst. This patient’s lung mass was an adenocarcinoma, a form of bronchogenic carcinoma.