(Figs.1 and 2)
(Fig. 3)
(Figs.1 and 2)
(Fig. 3)
Click on Images for Enlarged View
Findings: The CT scans shows dense parenchymal consolidation in the right lower lobe with air bronchograms (Fig 1.). Enhancing pulmonary vessels are seen within the consolidated lung (Fig 2). Multiple smaller nodular densities are seen in the contralateral lung (Fig 3).
Diagnosis: Bronchoalveolar carcinoma.
Discussion: In the patient with chronic pulmonary infiltrates, differential considerations should include lymphoma, sarcoid, lipoid pneumonia, and alveolar proteinosis. In the older patient, bronchoalveolar carcinoma should be a strong differential consideration.
Bronchioalveolar carcinoma is not generally associated with smoking. It is however, very often related to underlying scarring of the lung. Age of peak incidence is around 50 years of age, and occurs equally in both sexes. As the incidence of smoking decreases, the incidence of BAC has increased. Pathologically, BAC is characterized by its pattern of "lipedic growth". It appears to arise from type II pneumocytes. Because these cells produce mucin, a subgroup of patients present with bronchorrhea.
Radiologically, the most common presentation is as a solitary mass. It can also present as a unifocal or multifocal area of consolidation. If it presents as a solitary nodule, its prognosis is better than other types of lung cancer.
These tumors tend to be peripherally based, and there is often an air bronchogram sign reflecting the lipedic pattern of growth. As seen in this patient, the presence of enhancing vessels running through the areas of consolidation is the CT-angiogram sign. While thought to be characteristic of BAC, recent reports show that this sign can be seen in forms of pneumonia and other consolidative processes.
References:
Armstrong P, Wilson et al. Imaging of Diseases of the Chest.Mosby, 1996
Im JG, Han MC, Yu EJ: Lobar bronchioalveolar carcinoma: "angiogram" sign on CT.
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