Large cell acanthoma: a variant of solar lentigo with cellular hypertrophy

Background Large cell acanthoma (LCA) is an epidermal proliferation of enlarged keratinocytes. There is a lack of consensus on whether it represents a unique neoplasm or not. To determine whether it is a variant of solar lentigo, we compared macroscopic, microscopic and immunophenotypic attributes of LCA with conventional solar lentigo, seborrheic keratosis, actinic keratosis and Bowen disease. Methods We constructed tissue microarrays containing multiple cores of LCA, solar lentigo, seborrheic keratosis, actinic keratosis and Bowen disease. Tissue microarray sections were blindly analyzed for microscopic morphologic variables. Corresponding ex vivo dermoscopic images from the original cases were blindly analyzed for macroscopic morphologic variables. Immunostained sections from the tissue microarray were tested for keratin 10, keratin 5/6, Bcl‐2 and Ki‐67 expression by image analysis. Results There were no significant differences in the studied morphologic attributes between LCA and solar lentigo. All other tumor classes showed at least one significant morphologic difference with LCA. LCA and solar lentigo showed different keratin 10 and Bcl‐2 signal intensities. Conclusions LCA is best considered a variant of solar lentigo with cellular hypertrophy. The differences in immunophenotype and cell size could be because of differences in cell kinetics.