Immunohistochemical (IHC) staining for pS6 (serine 235/236 and serine 240/244) and PTEN was performed just before and during the everolimus re-treatment. All photographs were taken at 200 X magnification. Before everolimus re-treatment, the tumor cells exhibited strong positivity for pS6 in more than 50% of the tumor, whereas PTEN was weakly positive in tumor cells compared with the internal controls of endothelial cells (A). After 2 months of everolimus re-treatment, the tumor cells in the follow-up biopsy were completely negative for pS6. However, the intensity of PTEN was notably increased in all tumor cells (B).