The parallel finding that mouse S100A7/psoriasin was distinctively associated with areas of squamous differentiation within murine breast adenocarcinomas suggests that similar factors are involved in the regulation of both psoriasin/S100A7 and murine S100A7/psoriasin genes, and is in keeping with a similar role for the murine gene. Here, S100A7 is linked to breast adenocarcinoma.