Immunohistochemistry for Smads in paired tumor and normal pancreatic tissues. Upper panel shows the normal pancreatic tissue and the down panel shows the corresponding tumor tissue. Normal pancreas with strong focal and nuclear positivity (a. ×100) and tumor negative for Smad4 (b. ×400). Normal pancreas with strong diffuse cytoplasmic positivity (c. ×100) and tumor with moderate focal cytoplasmic positivity for Smad6 (d. ×200). Normal pancreas with strong diffuse cytoplasmic positivity (e. ×100) and tumor negative for Smad7 protein (f. ×200). (streptavidin- biotin immunoperoxidase).