Recently, pathological diagnosis, the gold standard for cancer diagnosis, has achieved superior performance by combining the Transformer with the multiple instance learning (MIL) framework using whole slide images (WSIs). However, the giga-pixel nature of WSIs poses a great challenge for the quadratic-complexity self-attention mechanism in Transformer to be applied in MIL. Existing studies usually use linear attention to improve computing efficiency but inevitably bring performance bottlenecks. To tackle this challenge, we propose a MamMIL framework for WSI classification by cooperating the selective structured state space model (i.e., Mamba) with MIL for the first time, enabling the modeling of instance dependencies while maintaining linear complexity. Specifically, to solve the problem that Mamba can only conduct unidirectional one-dimensional (1D) sequence modeling, we innovatively introduce a bidirectional state space model and a 2D context-aware block to enable MamMIL to learn the bidirectional instance dependencies with 2D spatial relationships. Experiments on two datasets show that MamMIL can achieve advanced classification performance with smaller memory footprints than the state-of-the-art MIL frameworks based on the Transformer. The code will be open-sourced if accepted.

通过将 Transformer 与多实例学习（MIL）框架结合使用整张切片图像（WSIs），我们提出了一种 MamMIL 框架，首次将选择性结构状态空间模型（即 Mamba）与 MIL 结合起来，实现了对实例依赖性的建模并保持了线性复杂性。在两个数据集上的实验证明，MamMIL 可以以比基于 Transformer 的最先进的 MIL 框架更小的内存占用来实现先进的分类性能。

MamMIL：基于状态空间模型的整片切片图像多实例学习