Collect images from a hospital (after removing the personal information). Then ask the doctors to annotate the images (normal/abnormal, bengin/malignant, location of mass, ....).
Is it enough to save image files with expert diagnose? or
save original files, expert diagnose and annotated image indicate region of interest (tumor area) and a program to calculate ROC curve for any computer algorithm perform diagnose automatic? like DRIVE data set for DR as an example