Tree-in-bud pattern

1. Universidade Federal do Rio de Janeiro, Rio de Janeiro (RJ) Brasil. 2. Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre (RS) Brasil. A 34-year-old female patient presented to the outpatient clinic with complaints of fever, cough, and weight loss (8 kg in the last 3 months). She had a history of having undergone resection of a uterine adenocarcinoma 2 years prior. A chest CT showed branching opacities, which characterize the tree-in-bud (TIB) pattern, in the middle lobe and the left lower lobe, as well as left lung volume reduction and consolidation with cavitation in the lingula (Figure 1). The TIB pattern represents centrilobular branching opacities, most pronounced in the lung periphery, resembling the budding of certain plants. Although, in most cases, the TIB pattern represents filling of bronchioles with mucus, pus, blood, or other materials, with or without dilatation, it may also be related to peribronchovascular connective tissue thickening or filling and dilatation of pulmonary arterioles. Although the TIB pattern is more commonly observed in bronchiolar infections (bronchopneumonia, infectious bronchiolitis, and endobronchial dissemination of tuberculosis), it has a broader differential diagnosis that includes bacterial infections, fungal infections (allergic bronchopulmonary aspergillosis), or viral infections; as well as bronchiectasis; idiopathic conditions (obliterative bronchiolitis and panbronchiolitis) or congenital conditions (cystic fibrosis); aspiration or inhalation of foreign material; and peripheral pulmonary vascular disease, especially due to endovascular metastatic spread of certain tumors. In our patient, the main differential diagnosis was between pulmonary tuberculosis and endovascular metastatic spread of the previously resected uterine tumor (neoplastic embolism).