  Histopathological images provide rich information for disease diagnosis.
Large numbers of histopathological images have been digitized into high
resolution whole slide images, opening opportunities in developing
computational image analysis tools to reduce pathologists' workload and
potentially improve inter- and intra- observer agreement. Most previous work on
whole slide image analysis has focused on classification or segmentation of
small pre-selected regions-of-interest, which requires fine-grained annotation
and is non-trivial to extend for large-scale whole slide analysis. In this
paper, we proposed a multi-resolution multiple instance learning model that
leverages saliency maps to detect suspicious regions for fine-grained grade
prediction. Instead of relying on expensive region- or pixel-level annotations,
our model can be trained end-to-end with only slide-level labels. The model is
developed on a large-scale prostate biopsy dataset containing 20,229 slides
from 830 patients. The model achieved 92.7% accuracy, 81.8% Cohen's Kappa for
benign, low grade (i.e. Grade group 1) and high grade (i.e. Grade group >= 2)
prediction, an area under the receiver operating characteristic curve (AUROC)
of 98.2% and an average precision (AP) of 97.4% for differentiating malignant
and benign slides. The model obtained an AUROC of 99.4% and an AP of 99.8% for
cancer detection on an external dataset.
