OBJECTIVETo provide ideal animal models for exploring pathogenesis and experimental therapy of primary malignant melanoma of the small intestine.

METHODSThe histologically intact primary and liver metastatic fragments derived from surgical specimens of one patient with metastatic malignant melanoma of the small intestine were orthotopically implanted in the small intestinal mucous layer of nude mice. The take rate, invasion and liver metastasis were observed. Morphology (light microscopy, electron microscopy), immunophenotype analysis, flow cytometry and karyotype analysis were applied for the original human tumors and the transplanted tumors.

RESULTSThe primary and liver metastatic fragments of malignant melanoma of the small intestine were successfully implanted in nude mice. After continuous passages in nude mice,an orthotopic model of human primary malignant melanoma of the small intestine(from the primary focus)in nude mice (termed HSIM-0501) and a liver metastatic model of human primary malignant melanoma of the small intestine (from the liver metastatic focus) in nude mice (termed HSIM-0502) were established. Histological examination of transplanted tumors revealed high-grade melanoma. S-100 protein and HMB45 were positive. Massive melanin granules and melanin complex were seen in cytoplasm of tumor cells.Chromosomal modal number was between 55 and 59. DNA index (DI) was 1.49-1.61, representing heteroploid. HSIM-0501 and HSIM-0502 were maintained for 25 and 27 passages in nude mice respectively. Three hundred and seventeen nude mice were used for transplantation. Both the take rate after transplantation and resuscitation rate of liquid nitrogen cryopreservation were 100%. HSIM-0501 exhibited 46.2% liver metastasis and 36.7% lymph node metastases. In HSIM-0502, both liver and lymph node metastases were 100%.The transplanted tumors autonomically and invasively grew in the small intestines of nude mice and hematogenous metastasis, lymph node metastasis and celiac planting metastasis occurred.

CONCLUSIONTwo nude mice liver metastatic models of human primary malignant melanoma of the small intestine are successfully established, which provide ideal animal models for the research of pathogenesis,metastasis biology and anti-metastatic experimental therapy of primary malignant melanoma of the small intestine.