1 Introduction  
2 Background  
2.1 Medical imaging techniques  
2.2 Public datasets  
2.3 Cancer detection issues  
3 Methodology  
4 Main investigation  
4.1 Framework challenges  
4.2 Annotation challenges  
4.3 Small interclass variance  
4.4 Class imbalance  
4.5 Small-scale lesion detection  
4.6 Occlusion  
4.7 Multitask learning  
4.8 Post processing  
4.9 Generalization  
5 Discussion  
6 Conclusion