Entropy-Regularized Attention for Explainable Histological Classification with Convolutional and Hybrid Models

Abstract

Deep learning models such as convolutional neural networks (CNNs) and vision transformers (ViTs) perform well in histological image classification, but often lack interpretability. We introduce a unified framework that adds an attention branch and CAM Fostering, an entropy-based regularizer, to improve Grad-CAM visualizations. Six backbone architectures (ResNet-50, DenseNet-201, EfficientNet-b0, ResNeXt-50, ConvNeXt, CoatNet-small) were trained, with and without our modifications, on five H&E-stained datasets. We measured explanation quality using coherence, complexity, confidence drop, and their harmonic mean (ADCC). Our method increased the ADCC in five of the six backbones; ResNet-50 saw the largest gain (+15.65%), and CoatNet-small achieved the highest overall score (+2.69%), peaking at 77.90% on the non-Hodgkin lymphoma set. The classification accuracy remained stable or improved in four models. These results show that combining attention and entropy produces clearer, more informative heatmaps without degrading performance. Our contributions include a modular architecture for both convolutional and hybrid models and a comprehensive, quantitative explainability evaluation suite.

Keywords: CAM Fostering; Grad-CAM; attention branches; convolutional neural networks; histological images; vision transformers.

Figure 1

Proposed methodology integrating ABN and CAM Fostering techniques.

Figure 2

Representative histological samples from each dataset.

Figure 3

Training process schematic of proposed method: feature extractor, attention branch, and perception branch with CAM Fostering.

Figure 4

Visual comparison of Grad-CAM heatmaps produced by baseline (left) and proposed (right) models. Rows correspond to different architectures: (a) ResNet-50, (b) DenseNet-201, (c) EfficientNet-b0, (d) ResNeXt-50, (e) ConvNeXt, and (f) CoatNet-small.