Tree in Bud Pattern – Differential Diagnosis

History: 50 year old male with cough.

Axial maximum intensity projection (MIP) of the chest in lung windows shows numerous branching opacities predominately in the periphery of the lung parenchyma with a classic “Tree in Bud” pattern.

This is the classic appearance of the “Tree in Bud” pattern seen on chest CT. The differential diagnosis for this pattern is broad, and includes infectious bronchiolitis (bacterial, viral, fungal), bronchiectasis, allergic bronchopulmonary aspergillosis, and aspiration pneumonia. Other more rare entities that can manifest in this pattern include bronchoalveolar carcinoma, intravascular metastases, cellulose granulomatosis, and capillary hemangiomatosis.