ERBB2 and idiopathic interstitial pneumonia: We observed costaining of the activated fibroblast (myofibroblast) marker, α-SMA within the fibrotic foci in the IPF lung sections, and activation (p-HER2) of HER2 in fibroblasts, although HER2/p-HER2 expression was also apparent in epithelial cells in normal lungs and in blood cells in IPF lungs (Fig. S4 D).