The Noguchi classification system for small adenocarcinomas has received considerable attention, particularly in Japan, but has not been nearly as widely applied and recognized as the WHO system. Mesothelioma Malignant solitary fibrous tumor. Type-I alvoelar adenomatoid malformation CAM has recently been identified as a precursor lesion for the development of mucinous AIS, but these cases are rare. Small adenocarcinoma of the lung.
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The objective of this essay was to describe and illustrate the CT findings that are most characteristic of these tumors. Three presentations are described: solitary pulmonary nodule, consolidation, and diffuse pattern. The last two should be included in the differential diagnosis, together with infectious diseases.
Knowledge of the various presentations and the use of proper diagnostic procedures are crucial to early diagnosis and to improving survival.
Keywords: Lung neoplasms; Adenocarcinoma, bronchiolo-alveolar; Tomography, X-ray computed. Introduction Adenocarcinoma is the most common histological type of cancer in various countries and has a wide spectrum of clinical, molecular, and pathological particularities, as well as of imaging patterns. Bronchioloalveolar carcinoma BAC is a subtype of adenocarcinoma showing an alveolar lepidic growth pattern along an intact interstitial framework but no vascular, stromal, or pleural invasion.
Nonmucinous BAC tends to present as a solitary lesion and has a better prognosis, whereas the mucinous subtype often presents with consolidation, has a propensity for dissemination, and has worse survival. This, together with the fact that many smokers present with severely impaired cardiopulmonary function, could explain the worse prognosis of lung neoplasms in these patients. Imaging patterns of BAC and adenocarcinoma with a bronchioloalveolar component Pulmonary nodule and focal ground-glass opacities A solitary pulmonary nodule, usually in the periphery of the upper lobes, is described as the most common CT finding in BAC and adenocarcinoma with a bronchioloalveolar component.
Ground-glass opacities raise a number of differential diagnoses, which range from benign diseases, such as focal fibrosis and lesions of an infectious nature, to pre-malignant opacities, such as atypical adenomatous hyperplasia AAH , and malignant lesions, such as BAC and adenocarcinoma with a bronchioloalveolar component.
Although most benign lesions tend to become smaller or disappear in three months, pre-malignant and malignant lesions can remain unchanged or grow Figure 3. However, it is of note that pure BAC might not show increased 18F-fluorodeoxyglucose FDG uptake, 6 given that these tumors are usually indolent, slow growing, and well differentiated.
Therefore, the lack of FDG uptake does not exclude the possibility of neoplasms, such as BAC, small lesions, and indolent cancers. Martins et al. Therefore, CT analysis is mandatory for the diagnosis Figure 5. Some findings, such as the angiogram sign, air bronchograms, ground-glass opacities, and air-space nodules Figure 6 , can be observed in BAC and in lobar pneumonia.
First described as being specific to the pneumonic form of BAC, the angiogram sign can be seen in numerous entities, such as infectious pneumonia, pulmonary edema, postobstructive pneumonia, lymphoma, and metastases. However, it should be emphasized that 18F-FDG-labeled glucose uptake might be absent in some cases of BAC or adenocarcinoma with a bronchioloalveolar component false negatives , and that PET can show false-positive results in inflammatory or infectious processes or both.
Consolidation, nodules Figure 9 , ground-glass opacities, air bronchograms, and cysts Figure 10 , as well as peripheral distribution and distribution in the lower lobes, characterize this pattern. The differential diagnosis should include other, benign, conditions, such as alveolar proteinosis, 18 hemorrhage, and infection.
For the evaluation of patients with the diffuse pattern of BAC, PET should be used, especially for staging and post-treatment follow-up Figure It should be borne in mind that 18F-FDG-labeled glucose uptake might be absent in some cases, a careful analysis of CT scans therefore playing an important role in the differential diagnosis and staging. Final considerations Both BAC and adenocarcinoma with a bronchioloalveolar component have a wide spectrum of CT patterns, such as solitary nodules or masses, ground-glass opacities, consolidation, and diffuse presentation.
Knowledge of the major imaging findings in these neoplasms is of utmost importance, especially for establishing an early diagnosis and differentiating such tumors from infectious pulmonary processes. Focal opacities, parenchymal consolidations that resolve slowly or show no significant change after treatment, or a combination of the two should raise the suspicion of BAC or adenocarcinoma with a bronchioloalveolar component.
In such situations, further diagnostic investigation is recommended in order to exclude lung neoplasms. For differential diagnosis or neoplasm staging, PET can be used. However, it should be emphasized that the method can yield false-negative and false-positive results, a careful analysis of the CT findings being therefore required in all cases.
References 1. The new World Health Organization classification of lung tumours. Eur Respir J. Prognosis and recurrent patterns in bronchioloalveolar carcinoma. Pictorial review of the many faces of bronchioloalveolar cell carcinoma. Br J Radiol. Evolving concepts in the pathology and computed tomography imaging of lung adenocarcinoma and bronchioloalveolar carcinoma.
J Clin Oncol. Bronchioloalveolar lung cancer: ACCP evidence-based clinical practice guidelines 2nd edition. Clinicopathological aspects of and survival in patients with clinical stage I bronchioloalveolar carcinoma. J Bras Pneumol. Bronchioloalveolar carcinoma: clinical, histopathologic, and radiologic findings. Small adenocarcinoma of the lung. Histologic characteristics and prognosis. CO;2- 9. Growth rate of small lung cancers detected on mass CT screening. Liebow AA.
Bronchiolo-alveolar carcinoma. Adv Intern Med. J Thorac Oncol. Radiol Bras. Illustrated Brazilian consensus of terms and fundamental patterns in chest CT scans. Ground-glass opacities on thin-section helical CT: differentiation between bronchioloalveolar carcinoma and atypical adenomatous hyperplasia.
Focal ground-glass opacity detected by low-dose helical CT. Malignant versus benign nodules at CT screening for lung cancer: comparison of thin-section CT findings. CT differentiation of pneumonic-type bronchioloalveolar cell carcinoma and infectious pneumonia. Maldonado RL. The CT angiogram sign. High-resolution CT findings of diffuse bronchioloalveolar carcinoma in 38 patients. E-mail: pedroptstorres yahoo. Submitted: 20 July Accepted, after review: 26 December Julia Capobianco Radiologist.
Gustavo Souza Portes Meirelles Radiologist.
Kagataur Adenocarcinoma in situ of the lung Services on Demand Journal. Bronquiklo the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License. The most common findings were: The new World Health Organization classification of lung tumours. When BAC recurs after surgery, the recurrences are local in about three-quarters of cases, a rate higher than other bronquioko of NSCLC, which tends to recur distantly. CT confirms extensive airspace opacities with numerous air-bronchograms. Sarcoma Lymphoma Immature teratoma Melanoma. These excluded tumors were reclassified as adenocarcinoma mixed type with predominant bronchioloalveolar pattern.
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