ALPaCA: Adapting Llama for Pathology Context Analysis to enable slide-level question answering

Large Vision Language Models (LVLMs) have recently revolutionized computational pathology. LVLMs transform pathology image embeddings into tokens recognizable by large language models, facilitating zero-shot image classification, description generation, question answering, and interactive diagnostics. In clinical practice, pathological assessments often require the analysis of entire tissue slides, integrating information from multiple sub-regions and magnification levels. However, existing LVLM frameworks have been restricted to the analysis of small, predefined regions of interest, lacking the ability to analyze pyramidal, gigapixel-scale whole-slide images (WSIs). In this work, we introduce ALPaCA (Adapting Llama for Pathology Context Analysis), and train the first general-purpose slide-level LVLM, leveraging 35,913 WSIs with curated descriptions alongside 341,051 question and answer pairs encompassing diverse diagnoses, procedures, and tissue types. By developing LongFormer, a vision-text interactive slide-level adaptor, and integrating it with a Gaussian mixture model-based prototyping adaptor, followed by training with Llama3.1, ALPaCA achieves superior performance in slide-level question answering, achieving over 90% accuracy in close-ended tests and high accuracy in open-ended questions as evaluated by expert pathologists, highlighting its potential for slide-level computer-aided diagnosis systems. Additionally, we show that ALPaCA can be readily fine-tuned on in-depth, organ-specific, or disease-specific datasets, underscoring its adaptability and utility for specialized pathology tasks.