Compared to the rest of pathologies analyzed, the immunohistochemistry assays revealed that only biopsies from IPF show a clear increment of AQP1 staining that localizes remarkably over hyperplasic cuboidal type II pneumocytes in the alveolar epithelium, and to a much lesser grade over few planar, hyperplasic or metaplasic type I cells (Figure 1). The gene discussed is AQP1; the disease is idiopathic pulmonary fibrosis.