Paraffin block preparation and immunohistochemical staining were performed using our previously described methods . Mouse anti-NBD1 immune serum diluted at 1:200 served as the primary antibody. Normal mouse serum was used as the negative control. Dako EnVision + System-horseradish peroxidase-labeled polymer anti-mouse IgG (Dako Cytomation, Glostrup, Denmark) diluted at 1:400 was used as the secondary antibody.