Group affinity weakly supervised segmentation from prior selected tissue in colorectal histopathology images

Precise tissue segmentation of histopathology images is often a crucial step in computational pathology pipelines. However, visual scoring by pathologists is sensitive and depends on their experience and perception. Therefore, there is a need for novel automatic systems to improve the accuracy and reproducibility of pathologists' interpretations. Here, a group affinity weakly supervised segmentation method (GAWS) is proposed to conquer this task, with the following pipeline. First, we create a cluster image by extracting the visual feature of each pixel using CNN and clustering it into different classes. Then, we create a target image by refining this cluster image with the constraints on prior tissue, color, and spatial distribution of pixels. Finally, a backpropagation process with a segmentation loss is considered to evaluate the error signals between cluster and target images and update the network parameters. We validate our method with extracellular mucin-to-tumor area quantification using a colorectal cancer clinical dataset with 163 Hematoxylin Eosin (H&E) whole slide images from 97 patients. Inter-observer agreement between pathologists and the proposed algorithm is excellent (ICC=0.917) and more accurate compared with two state-of-the-art unsupervised segmentation methods. Our results show that the GAWS results in a high average performance and excellent reliability when applied to histopathology images and possibly is a promising method for inclusion into clinical practice. This approach takes advantage of weakly supervised learning without any pre-trained network to have a tumor quantification tool that could improve the pathologist's workflow.

Automated summary

This study proposes a group affinity weakly supervised segmentation method (GAWS) for precise tissue segmentation of histopathology images. It creates cluster and target images by extracting visual features and applying constraints, and updates network parameters through backpropagation. The method shows excellent inter-observer agreement and accuracy in quantification of extracellular mucin-to-tumor area.