OBJECTIVE. Pulmonary carcinoid tumors are low-grade malignant neoplasms thought to arise primarily within the central airways in 85% of cases. The CT features of pulmonary carcinoid tumors that arise as solitary pulmonary nodules (SPNs) have not been well elucidated. We reviewed our experience with primary pulmonary carcinoid tumors to determine the distribution of lesions within the lung at diagnosis and to identify CT features that might aid in distinguishing these neoplasms from benign pulmonary nodules.
MATERIALS AND METHODS. CT scans, if available, of all patients with a primary pulmonary carcinoid tumor diagnosed by biopsy or surgical resection over the previous 15 years were reviewed. The CT scans were reviewed for the following features: lesion location; order of bronchus involved; lesion size, contour, and density; contrast enhancement; and the presence of peripheral atelectasis, hyperlucency, and bronchiectasis. We defined central lesions as those involved with a segmental or larger bronchus. Subsegmental bronchial involvement and tumors surrounded by lung parenchyma without direct airway involvement were defined as peripheral lesions. The final pathologic diagnosis for all cases was confirmed by review of cytologic or histologic specimens.
RESULTS. Twenty-eight carcinoid tumors were identified in 28 patients: 24 typical carcinoids and four atypical carcinoids. The study group was composed of 23 females and five males with a mean age of 52.4 years (range, 14–83 years). Twelve of the 28 lesions (43%) were central (i.e., involved a segmental or larger bronchus), and the remaining 16 lesions (57%) were peripheral. The mean tumor diameter for the 16 peripheral tumors was 14 mm (range, 9–28 mm); the majority (14/16, 88%) had a lobulated contour. Of six peripheral lesions with unenhanced and contrast-enhanced CT nodule enhancement studies, the mean maximal enhancement was 55.2 HU (range, 34–73 HU). Thirteen of the 16 peripheral carcinoid tumors (81%) involved a subsegmental bronchus, with 10 (63%) showing peripheral hyperlucency, bronchiectasis, or atelectasis.
CONCLUSION. In our series, primary pulmonary carcinoid tumors presenting as peripheral SPNs were more common than central endobronchial lesions in contrast to the published literature. The CT features of peripheral carcinoid tumors presenting as SPNs that suggest the diagnosis include lobulated nodules of high attenuation on contrast-enhanced CT; nodules that densely enhance with contrast administration; the presence of calcification; subsegmental airway involvement on thin-section analysis; and nodules associated with distal hyperlucency, bronchiectasis, or atelectasis.
OBJECTIVE. We retrospectively compared the CT findings of consecutive viral and bacterial lower respiratory tract infections (LRTIs) to determine their imaging appearance and any definable differences among the causative viruses and between the viral and bacterial infections.
MATERIALS AND METHODS. Imaging features of LRTI caused by influenza virus, respiratory syncytial virus (RSV), parainfluenza, adenovirus, and bacteria over a 33-month period were reviewed by three radiologists blinded to clinical and diagnostic information. Individual CT features and the dominant pattern of infection were recorded for each examination. Imaging characteristics were compared among the four respiratory viruses and between viral and bacterial infections.
RESULTS. One hundred fifteen chest CT scans were analyzed (60 influenza virus, 19 RSV, 10 adenovirus, four parainfluenza virus, and 22 bacterial pneumonia LRTIs). Individual imaging findings and imaging patterns were seen in similar frequencies when we compared viral and bacterial LRTIs, with the exception of the diffuse airspace pattern, which was seen more frequently in bacterial infections. Although there was overlap in the imaging appearance of individual viruses, RSV and adenovirus tended to have characteristic imaging appearances. RSV presented with an airway-centric pattern of disease (13/19 cases [68%]) characterized by varying mixtures of tree-in-bud opacities and bronchial wall thickening, with or without peribronchiolar consolidation. Adenovirus typically appeared as multifocal consolidation or ground-glass opacity without airway inflammatory findings (7/10 cases [70%]).
CONCLUSION. There is considerable overlap in the imaging appearance of viral and bacterial respiratory infections. However, some characteristic differences can be seen, especially with RSV and adenovirus infections.
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