Generation of GIST xenografts. Tumor was xenografted into the livers, kidneys, lesser sacs and gastric walls of NOD-scid and NSG mice. Using ultrasound, we followed tumor progression. A. At 4 weeks, one tumor in the liver increased from 4 × 2 mm to 7 × 2.4 mm based upon ultrasound examination. B-C. At 7 weeks, the same mouse became distressed and we performed a necropsy with passage of the tumor into two NOD-scid mice. The tumor is noted at the end of the cotton swab. 6-0 silk suture material can be seen at the site of implantation.