CT and x-ray signs point to pulmonary pathologies

Patterns in radiological images can help with the identification and differential diagnosis of selected processes.1,2 Such signs should be recognizable, having a characteristic appearance that can identified. Several radiological signs can be of use when diagnosing pulmonary pathology: the crazy-paving sign, the golden "S," the gloved finger, the halo sign, the deep sulcus sign, the incomplete border, the luftsichel and scimitar signs, and the leafless tree. Crazy-paving sign. This pattern, seen on thin-section CT images of the lungs, is characterized by a reticular pattern superimposed on ground-glass, resembling a path that has been made with broken pieces of paving (Figure 1). The reticular pattern is believed to result from a thickening of the interlobular septa, while the areas of ground-glass opacity result from partial alveolar filling processes.3 The crazy-paving sign was initially recognized in patients with pulmonary alveolar proteinosis, though it may be seen in patients with other diseases. The differential diagnosis includes Pneumocystis jiro-veci pneumonia, mucinous bronchioloalveolar carcinoma, sarcoidosis, lipoid pneumonia, adult respiratory distress syndrome, and pulmonary hemorrhage. Golden "S." This finding is seen on posteroanterior chest radiographs when a large central mass produces partial collapse of the right upper lobe. As the lobe collapses, the minor fissure moves superiorly and medially toward the mediastinum. The collapsed lobe is visible as a concave triangular opacity, while the central mass forms a convex bulge at the origin of the lobe. The combination resembles a reverse "S" shape (Figure 2). The golden "S" sign should always raise suspicion of a central neoplasm, such as primary bronchial carcinoma. Other central masses to consider include metastasis, primary mediastinal tumor, and enlarged lymph nodes. Although initially used to describe right upper lobe collapse, the golden "S" sign can be applicable to atelectasis involving any lobe.4 Gloved finger. Visible on conventional chest radiographs and CT images, this sign is characterized by branching fingerlike opacities that originate from the hila and are directed peripherally (Figure 3). These opacities represent dilated bronchi filled with mucus (mucoid impaction). The lung distal to the mucoid impaction remains aerated by collateral air drift through the interalveolar pores and the canals of Lambert, allowing the dilated bronchi to be seen.5 Bronchial impaction may be secondary to obstructive and nonobstructive processes. Any obstructing lesion can lead to distal bronchiectasis and mucoid impaction. The most common benign lesions that cause bronchial obstruction are hamartoma and lipoma. Malignant neoplasms most likely to lead to obstruction are bronchogenic carcinoma and carcinoid tumors. Some other, less common, causes of obstruction are congenital bronchial atresia, broncholithiasis, and aspirated foreign bodies. Non-obstructive causes of bronchial impaction include allergic bronchopulmonary aspergillosis; asthma; and cystic fibrosis, with or without associated allergic bronchopulmonary aspergillosis. Halo sign. Visible on CT studies, this refers to a zone of ground-glass attenuation surrounding a pulmonary nodule or mass (Figure 4). The presence of such a halo is usually associated with hemorrhagic nodules. The halo sign was initially described in patients with invasive aspergillosis.6 It may also occur with other infections, such as viral pneumonia, and in other conditions associated with pulmonary hemorrhagic nodules, such as lung metastases from hypervascular tumors (angiosarcoma, choriocarcinoma, and osteosarcoma), pulmonary Kaposi sarcoma, or Wegener's granulomatosis. The halo sign may be seen in cases of lepidic tumoral growth, where tumor cells spread along the