AIM:To establish a nude mice model of human hepatocellularcarcinoma(HCC)via orthotopic implantation of histologicallyintact tissue,in order to study biologic features of HCC invivo and to direct clinical treatment respectively.METHODS:Histologically intact fresh specimens of HCCwere orthotopically implanted in nude mice (BALB/c,nu/nu).Survival rate and growth curve were investigated with B-ultrasound.Morphological characteristics of pathology andspontaneous metastatic rates were detected with microscopy.Expression of multidrug resistance genes studied withimmunohistochemical method and RT-PCR,and other biologicfeatures of implanted tumor were observed and comparedwith human HCC specimens.RESULTS:Out of the specimens from two patients withHCC,only one specimen survived in nude mice.The orthotopicimplantation tumor survival rate,spontaneous intrahepaticmetastatic rate,pulmonary metastatic rate and bonemetastases rate were 100%,75.0%,37.5% and 37.5%respectively in the first passage.AFP was kept on secretingand increasing with the size of the tumor.The morphologicalcharacteristics and biologic features were similar to thedonor’s,the protein and mRNA of MDR1 and LRP wereexpressed in tumors of the model and the donor,and therewas no significant difference between them(P>0.05).CONCLUTION:The model of nude mice with orthotopicimplantation of histologically intact HCC tissue is an idealmodel to study biologic features of HCC in vivo and to directclinical treatment.Gao YS,Chen XP,Li KY,Wu ZD.Nude mice model of humanhepatocellular carcinoma via orthotopic implantation ofhistologically intact tissue.World J Gastroenterol 2004;10(21):3107-3111http://www.wjgnet.com/1007-9327/10/3107.asp AIM: To establish a nude mice model of human hepatocellular carcinoma (HCC) via orthotopic implantation of histologically inactic tissue, in order to study biologic features of HCC invivo and to direct clinical treatments respectively. METHODS: Histologically intact fresh specimens of HCCwere orthotopically implanted in nude mice (BALB / c, nu / nu). Survival rate and growth curve were investigated with B-ultrasound. Morphological characteristics of pathology and parastaneous metastatic rates were detected with microscopy. Expression of multidrug resistance genes studied with immunohistochemical method and RT-PCR, and other biologic features of implanted tumors were observed and comparedwith human HCC specimens .RESULTS: Out of the specimens from two patients with HCC, only one specimen survived in nude mice. orthotopicimplantation tumor survival rate, spontaneous intrahepatic metastatic rate, pulmonary metastatic rate and bonemetastases rate were 100% 75.0%, 37.5% and 37.5% respectively in the first passage. AFP wa s kept on secreting and increasing with the size of the tumor. Morphological characteristics and biologic features were similar to the donor’s, the protein and mRNA of MDR1 and LRP wereexpressed in tumors of the model and the donor, and there was no significant difference between them (P> 0.05) .CONCLUTION: The model of nude mice with orthotopic implantation of histologically intact HCC tissue is an ideal model to study biologic features of HCC in vivo and to direct clinical treatment. Gao YS, Chen XP, Li KY, Wu ZD. Nude mice model of human hepatocellular carcinoma via orthotopic implantation ofhistologically intact tissue. World J Gastroenterol 2004; 10 (21): 3107-3111http: //www.wjgnet.com/1007-9327/10/3107.asp