Bronchioloalveolar carcinoma and the air bronchogram sign: a new pathologic explanation

Bronchioloalveolar carcinoma (BAC) is one of the few lung tumors known to demonstrate the air bronchogram sign. Production of this valuable radiologic sign by this tumor has been ascribed to an "alveolar" filling process in which tumor grows along alveolar walls with preservation of the architecture and secretes copious amounts of mucus. Thus, aerated bronchi are surrounded by alveoli that are filled with mucus and tumor. We present a case in which the air bronchogram sign and pulmonary consolidation are associated with a nonsecretory BAC. Alternative mechanisms that may produce the air bronchogram sign in BAC are offered.