Establishment Of Axillary Lymph Node Metastasis Of Breast Cancer Model In Animal And Contrast-enhanced Ultrasound Study

Objective To establish breast cancer model with axillary lymph node metastasis in nude mice using MDA-MB-231 cell lines and xenografted tumor masses, and observe tumors in situ and lymph nodes in axillary through contrast-enhanced ultrasound(CEUS).Methods Divided twelve female nude mice of five weeks into A, B groups randomly. A group had seven nude mice, B group had five nude mice. A group nude mice were injected with MDA-MB-231 cells suspension into the second right mammary fat pad. Two weeks after emerged tumors,the orthotopic tumors of two nude mice of A group were dissected and then implanted into the second right mammary fat pad of B group nude mice. The other mice of A group continued to be fed. Viewed the tumors in situ and lymph nodes in homolateral axillary through general observation and conventional ultrasound. After six weeks of inoculation, every mice was injected 0.1ml ultrasound contrast agent of SonoVue in tail vein and subcutaneous around tumors. When the CEUS over, we excised the tumors and the swollen lymph nodes in right axilla of all nude mice to make pathological examination.Results(1)A group have a 7/7 tumor formation rate seven days after implanted, B group was 5/5 five days after implanted.(2)The tumor volumes between the two groups had evident difference(P=0.023), and the tumor volume of B group was bigger than A group.(3)The tumors showed abundant blood flow and emerged necrosis area later under conventional ultrasonic observation. No lymph node was found with general observation and conventional ultrasound.(4)After rat tail intravenous contrast-enhanced ultrasound examination, the tumors in situ of all mice showed heterogeneous enhancement. After CEUS through subcutaneous tissue around tumors, one lymph node in axillary of one mice in B group appeared heterogeneous enhancement, the detection rate of CEUS to discover axillary lymph node was 1/4 and the accuracy rate was 1/1 when made the pathological results as the gold standard.(5)The result of pathology in the two groups testified the tumors were invasive ductal carcinoma. A group had three nude mice which had one tumid lymph node respectively(reactive hyperplasia lymph nodes), the lymph node enlargement rate was 3/5; B group had one nude mice that had one tumid lymph node(metastatic lymph node), the lymph node enlargement rate was 1/5, the lymph node enlargement rate between the two groups showed no significant difference(P=0.524).Conclusions Use the method of orthotopic implantation with MDA-MB-231 xenografted tumor mass can generate newborn axillary lymph node and establish breast cancer model with lymph node metastasis in nude mice, can provide a useful mean to research the lymph node metastasis mechanism of breast cancer. CEUS is valuable in the diagnosis of metastatic lymph node of breast cancer model, it can display the blood flow distribution in the tumor and judge the tumor necrosis accurately, it can monitor the process of tumor metastasis real-timely, dynamically, simply and effectively, display the newborn lymph vessel and lymph node, and lay the root for the study of ultrasound microbubble carrying gene or drug to inhibit tumorous lymphatic metastasis.