Small, irregular clusters of Sp-C positive cells that don’t disrupt aveolar architecture were classified as atypical adenomatous hyperplasia (AAH), larger, cohesive clusters of Sp-C positive cells that disrupt aveolar architecture were classified as adenomas (AD), large clusters of Sp-C positive cells with irregular borders and/or heterogeneous SpC expression, and including cells with irregularly sized nuclei, were classified as adenocarcinomas (AC) [33]. Here, SFTPC is linked to adenocarcinoma.