Gross images of liver tumors. The figures show the overall appearance and cross sections of the liver tumors developed in tree shrews 98–2 (left) and 121–1 (right) respectively. Generally, both tumors were solitary nodule and oval in shape, with uneven and mottled surface. The textures of the tumors were brittle. The cross sections of the nodules were nonuniform in color, mostly grayish white (lower left) or dark red (lower right). The three arrows in each picture point the edge of the tumor. The scale in each picture indicates tumor size.