Objective To develop a computer-aided diagnosis(CAD)system with automatic contouring and morphologic and textural analysis to aid on the classification of breast nodules on ultrasound images.Methods A modified Level Set method was proposed to automatically segment the breast nodules(46malignant and 60benign nodules).Following,16morphologic features and 17texture features from the extracted contour were calculated and principal component analysis(PCA)was applied to find the optimal feature vector dimensions.Fuzzy C-means classifier was utilized to identify the breast nodule as benign or malignant with selected principal vectors.Results The performance of morphologic features was 78.30%for accuracy,67.39%for sensitivity and 86.67%for specificity,while the latter was 72.64%,58.70%and 83.33%,respectively.After the combination of the two features,the result was exactly the same with the morphologic performance.Conclusion This system performs well in classifying the malignant breast nodule from the benign breast nodule. Objective To develop a computer-aided diagnosis (CAD) system with automatic contouring and morphologic and textural analysis to aid on the classification of breast nodules on ultrasound images. Methods A modified Level Set method was proposed to automatically segment the breast nodules (46 maignant and 60 benign Fold, 16morphologic features and 17texture features from the extracted contour were calculated and principal component analysis (PCA) was applied to find the optimal feature vector dimensions. Fuzzy C-means classifier was utilized to identify the breast nodule as benign or malignant with selected principal vectors. Results The performance of morphologic features was 78.30% for accuracy, 67.39% for sensitivity and 86.67% for specificity, while the latter was 72.64%, 58.70% and 83.33% respectively. After the combination of the two features, the result was exactly the same with the morphologic performance. Confluence This system performs well in classifying the malignant breast nodule f rom the benign breast nodule.