Application of transfer learning and ensemble learning in image-level classification for breast histopathology

Background: Breast cancer has the highest prevalence among all cancers in women globally. The classification of histopathological images in the diagnosis of breast cancers is an area of clinical concern. In computer-aided diagnosis, most traditional classification models use a single network to extract features, although this approach has significant limitations. Moreover, many networks are trained and optimized on patient-level datasets, ignoring lower-level data labels. Method: This paper proposes a deep ensemble model based on image-level labels for the binary classification of breast histopathological images of benign and malignant lesions. First, the BreaKHis dataset is randomly divided into training, validation, and test sets. Then, data augmentation techniques are used to balance the numbers of benign and malignant samples. Third, based on their transfer learning performance and the complementarity between networks, VGG16, Xception, ResNet50, and DenseNet201 are selected as base classifiers. Results: In a ensemble network model with accuracy as the weight, the image-level binary classification achieves an accuracy of 98.90%. To verify the capabilities of our method, it is experimentally compared with the latest Transformer and multilayer perception (MLP) models on the same dataset. Our ensemble model shows a a 5%–20% advantage, emphasizing its far-reaching abilities in classification tasks. Conclusion: This research focuses on improving the performance of a classification model with an ensemble algorithm. Transfer learning has an essential role in classification of small datasets, improving training speed and accuracy. Our model outperforms many existing approaches with respect to accuracy and has applications in the field of auxiliary medical diagnosis.