<P> In radiology, the tree - in - bud sign is a finding on a CT scan that indicates some degree of airway obstruction . </P> <P> The tree - in - bud sign is a nonspecific imaging finding that implies impaction within bronchioles, the smallest airway passages in the lung . The differential for this finding includes malignant and inflammatory etiologies, either infectious or sterile . This includes fungal infections, mycobacterial infections such as tuberculosis or mycobacterium avium intracellulare, bronchopneumonia, chronic aspiration pneumonia, cystic fibrosis or cellular impaction from bronchovascular spread of malignancy, as can occur with breast cancer, leukemia or lymphoma . It also includes lung manifestations of autoimmune diseases such as Sjogren's syndrome or rheumatoid arthritis . </P>

Tree in a bud appearance in ct scan