Histological examination of subcutaneous tumors in Balb/c mice. L-SPIO loaded CT-26 cells were injected into the dermis of Balb/c mice to form tumors. Sections of the subcutaneous tumor growing from inoculated L-SPIO-loaded CT-26 cells are indicated. Histochemical H/E staining showed proliferation cells at central (A) and peripheral regions (B) of the tumor nodule growing from L-SPIO-loaded CT-26 cells. (200× magnification).