The 125I-mAb mixture was synthesized with a radiolabeling efficiency of >60 and >85%, and the radioactivity was detected by whole body gamma camera imaging as early as 1 h p.i. in SK-LMS-1 (human leiomyosarcoma with high expression of c-MET) and S-114 (NIH 3T3 cells transformed with human HGF and human c-MET) murine models, whereas initial visualization of tumors in M-114 and DA3 murine models were at 1 day p.i. (M-114, NIH 3 T3 cells transformed with murine HGF and murine c-MET; DA3, mouse mammary carcinoma expressing murine c-MET). The gene discussed is HGF; the disease is leiomyosarcoma.