The Value Of Sonographic Elastography In The Differential Diagnosis Of Axillary Lymph Nodes In Breast Cancer

Background and purpose Breast cancer is one of the most common malignant tumors in women, its incidence rate has continued to rise in recent years. The status of axillary lymph node is important on the prognosis, and is a important factor for clinical choice of treatment. Axillary lymph node dissection (ALND) in patients is critical in the breast cancer staging, prognosis and treatment effect, but this procedure is time-consuming and can cause numerous postoperative problems, such as lymphedema, pain, impaired shoulder mobility, and arm weakness etc.it is not necessary for patients without axillary lymph node metastasis. Some researchs show that nomal lymph node chain play a role in block the spread of the cancer, unnecessary ALND may weaken the immunity in breast cancer women.In the field of surgical treatment of breast cancer, Sentinel lymph node biopsy (SLNB) is interesting. Research shows that SLNB could predict axillary lymph node status accurately. The sentinel lymph node (SLN) detection methods include blue dye method, radionuclide method and their combination. The combination of blue dye method and the the radionuclide method can improve the accuracy of SLNB, and reduce the false negative rate. Although SLNB technique is mature, but unable to replace axillary lymph node dissection, For the following reasons:①The effect of SLNB application depends largely on the surgeon’s professional standards,②The false negative is inevitable due to the skip metastasis of axillary lymph nodes.③15%of patients have two or more SLN, it is relatively difficult to check multiple SLN observed without Medical instrument.④SLNB is invasive and radiological examination, SLN examination have adverse impact on both doctors and patients and the treatment.Preoperative axillary lymph node status may avoid unnecessary axillary lymph node dissection, and without sentinel lymph node biopsy. Traditional technique judge lymph node states on morphology indicators, such as L/S, shape, the thickness of the cortex, Vascular patterns. There is controversial in the morphological indicators diagnosis of axillary lymph nodes. Its morphology may be normal but Metastatic lymph node. And lymph nodes size will change not only due to Malignant invasion, but also inflammatory reactive hyperplasia. There is a certain cross-overlap between the the transfer and the non-transfer constituency.A variety of imaging means to judge the states of the axillary lymph node, Computer tomography (CT) can demonstrate the lymph node clearly, but have much radiation. Magnetic resonance imaging (MRI) resolution is high, little radiation injury, but check procedures are complicated, time-consuming and expensive. Positron emission tomography (PET) judged axillary lymph node metastasis from the point of view of molecular metabolism. Lymph nodes to determine the nature can provide more information, but the spatial resolution is low, there are some false negative. At the same time inflammatory reactive lymph node hyperplasia and other diseases because of its metabolism, can be expressed as a false positive, and that means there are also expensive, radioactive. Conventional ultrasound is simple, convenient, noninvasive which is a common method to evaluate of axillary lymph nodes nature. Determine the performance of axillary lymph node nature based on conventional sonographic accuracy is not enough, and the lack of uniform standards, reported in the literature routine ultrasound axillary lymph node false negative rate of up to33%.Elastography is a new ultrasound technique developed in recent years. That measures the charactertistics of tissue compliance. It allows assessment of elasticity distribution in hardness between diseased tissue and normal tissue. Therefore, by measureing tissue strain induced by compression.we can estimate tissue hardness. Tissue elasticity resulting from compression is displayed as an image called an elastogram. and malignant tissue is generally harder than normal tissue, elastography might provide clinical information.In this study, the method of conventional ultrasound, elastography and combined, to explore the role of different ultrasound technique determine the nature of axillary lymph nodes. Further application Logistic regression analysis model to explore the variety of sonographic characteristics and axillary lymph node metastasis in the axillary lymph nodes, in order to filter out sensitive indicators identify breast cancer metastatic lymph nodes.Materials and methodsFrom May2012to December2012,60breast cancer patients with84axillary lymph nodes underwent axillary Conventional sonography and sonographic elastography. The histologic diagnosis was used as the reference standard, all patients are female, age31-73, The mean age of the patients was47±9years.Using Hitachi digital HIVISION Preirus ultrasound system,6-13MHZ high-frequency linear transducer was used in this study. The elastographic study was performed with the patient lying in the same position used for conventional breast sonography. The patient elevated the affected arm and lifted the affected thorax, conventional sonography Focus on the axillary lymph node L/S, thickness of the cortex, Vascular patterns and so on. After identification of the most suspicious axillary lymph node on B-mode sonography, elastographic images of the lymph node were obtained with continuous manual compression. To even compression of the target axillary lymph node, we set the region of interest to exclude pectoralis muscles and axillary vessels. We applied the probe with only light pressure, perpendicular to the skin. Real-time elastographic images were then saved and by Two radiologists analyzed the B-mode sonographic and elastographic images. Choose the most suspicious lymph nodes and markers, ensure that is a representative sample. Some axillary lymph nodes were excluded for the following reasons:Multiple lymph nodes Together; The depth of the axillary lymph node is greater than3cm; necrosis; the patients underwent preoperative chemotherapy and/or radiotherapy; systemic infection skin diseases; histopathologic results were unsatisfactory and the patients were lost to follow-up.The vascular pattern of lymph nodes was described as none, central, peripheral, or mixed. None vascularity was defined as all lymph node showed no color flow signal;Central vascularity was defined as a simple hilar vessel signal or centrifugal branches; peripheral vascularity was defined as circumferential linear vascularity along the periphery of the node; and mixed vascularity was defined as more than one vascular pattern in a node, none, central as reactivity and peripheral, mixed as metastatic.color flow features reference Alder classification standard, On a three-level scale of low to marked vascularity. level0:no blood flow signals or a little in the lymph nodes. Level1:1-2dot color flow.Level2:3-4dot color flow or1vessel clear blood flow; Level3:4or more visible dotted blood flow or2vessels clear blood flow; Level0,1as the reactivity, level2,3as metastatic.Conventional sonography scores were determined as the sum of the4criteria: long to short-axis diameter ratio (<2.0, score1;≥2.0, score2), and cortical thickening (<0.3cm, score1;>0.3cm, score2). classification of color flow (level0,1,score1; level2,3, score2). Vascular patterns (None or central, score1; peripheral or mixed, score2). We classified the lymph nodes depends on the above criteria combined.Elastographic images were given1of4elasticity scores based on the percentage*and distribution of the lymph node areas with high elasticity (blue area):score1, absent or very small blue area; score2, blue area less than45%ofthe lymph node; score3, blue area45%of the lymph node or greater; and score4, blue area with or without a green rim.Statistical analysis was performed using SPSS13.0software. To identify statistically significant differences between mean values, we used t test in the elasticity imaging and the SR. Receiver operating characteristic curve analysis were performed. All standard calculations for the sensitivity, specificity. And the above several methods were compared uses the McNemar test. The Az values were calculated and compared for the Conventional sonography, elastography, and combined. Statistically significant differences between Az values are compared using Z test.Data was subjected to univariate and multivariate logistic regression. We took conventional ultrasonography and Ultrasonic Elastography Characteristics(L/S, cortical thickness, classification of blood supply, resistance index, Vascular patterns, the elasticity score, strain ratio)into account. With pathologic diagnosis as the golden standard,p<0.05indicated statistical significance.ResultsOf a total of84axillary lymph nodes,34were reactive, and50were metastatic.1.The Elasticity score for metastatic axillary lymph nodes (mean±SD,3.0±0.83)was significantly larger than the score for reactive axillary lymph nodes (1.8±0.87).2. The sensitivity, specificity of Conventional ultrasound distinguish between benign and malignant axillary lymph node were74.0%,64.7%. The sensitivity,specificity of Elasticity score distinguish between benign and malignant axillary lymph node were82%,61.8%. The sensitivity,specificity of Conventional ultrasound combined with ultrasound elastography distinguish between benign and malignant axillary lymph node were86%,73.5%.3. The Az values were0.782for Conventional ultrasound,0.812for elastography,and0.858for the combined, the combined Have significance difference compared to others.Indicate that the combined method is helpful to improve the sensitivity of the axillary lymph nodes nature. The Az order for conventional ultrasound combined with Elasticity score> Elasticity score> conventional ultrasound, combined method compared with alone has significant difference (Z=2.131, P<0.05, compared with conventional ultrasonic; Z=1.996, P<0.05,compared with Elasticity score), conventional ultrasound combined with Elasticity score improve the diagnostic value of axillary lymph node properties, there was no significant difference between conventional ultrasound and Elasticity score (Z=1.6, P>0.05), showed that elasticity score is not better than conventional ultrasonic diagnosis. 4. The SR for metastatic axillary lymph nodes (3.3±2.9) was significantly larger than the score for reactive axillary lymph nodes (1.8±1.0). we selected SR=2.3as the cutoff point, The sensitivity,specificity of SR distinguish between benign and malignant axillary lymph node were76.0%,80.6%. and Az values were0.824.5. Univariate analysis showed that axillary lymph node L/S, thickness of the cortex, Vascular patterns, the elasticity score and strain ratio5factors associated with axillary lymph node metastasis of breast cancer (P<0.05). Multivariate logistic regression show that cortical thickness, L/S, strain ratio and Vascular patterns4factors are risk factors of axillary lymph node metastasis breast cancer (P<0.05), and OR value29.899、14.020.6.166.4.696respectively, of which the cortical thickening of the biggest correlation with lymph node metastasis of breast cancer.Conclusions1. Conventional ultrasound combined with ultrasound elasticity score can improve the accuracy of the diagnosis of benign and malignant axillary lymph nodes.2. Single factor analysis showed that axillary lymph node L/S, thickness of the cortex, Vascular patterns, the elasticity score and strain ratio5factors associated with axillary lymph node metastasis of breast cancer (P<0.05). Multiariable Logistic regression results show that cortical thickness, L/S, strain ratio and Vascular patterns factors is risk factors of axillary lymph node metastasis in breast cancer (P<0.05), of which the cortical thickening of the biggest correlation with lymph node metastasis of breast cancer.3. Elasticity index (SR) imaging is enter the Logistic regression model, the predictive value of axillary lymph node properties has no obvious advantage compared with conventional ultrasound, so combined use inspection techniques and multiple index comprehensive judgment, will help to improve the accuracy of the diagnosis of axillary lymph node properties.