Fig. 6

Potential explanations of how deep networks identified tissue source institutions even without explicit training. a Tissue patches of WSIs provided by the institution “Indivumed Inc” were accurately identified by using DenseNet’s and KimiaNet’s deep features, perhaps due to their unique stain intensities and color spectrum. One can observe that they have a dominant purplish stain. b Digital pathology images are generally noisy. The noise could be amplified by histogram equalization techniques. Although those noisy patterns are more prominent in the background, they most likely exist over the tissue area as well. c Convolutional layers could easily pick up noisy patterns existing in a background patch, and over-emphasizing them, as shown by visualizing the output of a convolutional layer of KimiaNet