Epithelial cells covering intra-alveolar fibroblastic polyps (Masson's bodies) in OP/COP samples variably expressed LAM5γ2 (Fig. 4), never exhibited the sandwich pattern observed in UIP, and were characterised by an alveolar pneumocyte immunophenotype (SPA+, CK5-negative, ΔN-p63-negative). This evidence concerns the gene KRT5 and idiopathic pulmonary fibrosis.