Squamous cell lung carcinoma with surrounding pure nonmucinous bronchioloalveolar carcinoma (BAC)

Bronchioloaveolar cell carcinoma (BAC) was defined by the WHO in 1999 to be a subtype of adenocarcinoma with a pure bronchioloalveolar growth pattern showing no evidence of stromal, vascular, or pleural invasion [Travis WD, Colby TV, Conin B, et al. Bronchioloalveolar carcinoma. In: Sobin LH, editor. WHO international histological classification of tumors, 3rd ed. Copenhagen, Denmark: Springer; 1999. p. 34–8]. Although there were some reports that BAC was presented together with squamous cell carcinoma, this is the first report that it might be transformed from surrounding pure nonmucinous BAC. Physicians should be aware that pure BAC could transform to squamous cell carcinoma, and that such cases might not respond to gefitinib.