Bronchioalveolar cell carcinoma: radiologic appearance and dilemmas in the assessment of response.

Bronchioalveolar cell carcinomas (BACs), a subset of primary lung adenocarcinomas, are uncommon. Histologically, they are a diverse group of malignancies. The diagnosis is restricted to adenocarcinomas that grow in a lepidic manner and that have no stromal, vascular, or pleural invasion. Their histologic diversity leads to varied radiologic manifestations that are often indistinguishable from those of other primary non-small-cell lung cancers (NSCLC). However, typical manifestations, many of which can be attributed to lepidic growth, have been reported. Radiologic manifestations include a solitary peripheral pulmonary nodule, airspace disease, and multiple nodules and a combination of these findings can be present in a single patient. The most common manifestation, a solitary pulmonary nodule, is usually indistinguishable from other primary NSCLC. However, pseudocavitation and air bronchograms within the nodule can be useful in suggesting the correct diagnosis. In addition to aiding in the diagnosis of BAC, radiologic imaging is an important component in the evaluation of the therapeutic efficacy of treatment; serial measurements of tumor size before and after treatment are commonly used to assess response. However, BACs that are consolidative or ground-glass in nature present challenges in tumor-response determination. Other imaging modalities, such as positron emission tomography scanning, may prove helpful in assessing the metabolic response to therapy but have yet to be proven effective.