SLC4A1 and neoplasm: AE1/AE3+ stained focal keratin-positive cells and small duct-like structures within these foci; it could not be determined whether these positively stained cells represented residual tumor cells, small admixed regenerative blood vessels with keratin-labeling of the endothelial lining, or reactive, regenerative, and atrophic non-neoplastic lung parenchyma (Fig. 6).