Radiographic imaging of bronchioloalveolar carcinoma: Screening, patterns of presentation and response assessment

Bronchioloalveolar carcinoma (BAC) is a previously uncommon subset of adenocarcinoma with unique epidemiology, pathology, radiographic presentation, clinical features, and natural history compared with other non-small cell lung cancer (NSCLC) subtypes. Classically, BAC demonstrates a relatively slow growth pattern and indolent clinical course. However, in a subset of patients, rapid growth and death from bilateral diffuse consolidative disease occurs within months of diagnosis or recurrence. Recent data suggest that the incidence of BAC is increasing, notably in younger nonsmoking women. The initial radiographic presentation of BAC varies considerably, from single ground glass opacities (GGOs) or nodules of mixed ground glass and solid attenuation to diffuse consolidative or bilateral multinodular disease. The rising incidence of BAC is also reflected in recent lung cancer screening studies employing helical computed tomography (CT), where the differential diagnosis of GGOs includes not only BAC and overt adenocarcinoma, but inflammatory disease, focal fibrosis, and atypical adenomatous hyperplasia. Because advanced-stage BAC presents as measurable mass lesions in fewer than 50% of cases, determination of radiographic response to therapy by standard criteria is often difficult. Here, we review current data regarding the radiographic imaging of BAC: its radiographic presentations in asymptomatic early-stage and in advanced-stage disease, the functional imaging characteristics of BAC, and challenges of response assessment, including evolving opportunities for computer-assisted image analysis.