Fig. 8
From: Fibrosing pneumonia – how to diagnose, and how to recognize the etiology?
UIP/IPF case, showing transition of epithelial or mesenchymal cells: TTF1 nuclear staining characterizes epithelial cells, whereas red filamentous staining for smooth muscle actin characterizes myofibroblasts. Arrows show cells coexpressing both markers. If these cells show epithelial-to-mesenchymal or mesenchymal-to-epithelial transition cannot be evaluated by morphology – both options might work. Magnification, X400