To help answer these questions, biopharma companies rely on expert pathologists to analyze slides and help evaluate the questions they might have. 
As you might imagine, it takes an expert board certified pathologist to make accurate interpretations and diagnosis. In one study, a single biopsy result was given to 36 different pathologists and the outcome was 18 different diagnoses varying in severity from no treatment to aggressive treatment necessary. Pathologists also often solicit feedback from colleagues in difficult edge cases. Given the complexity of the problem, even with expert training and collaboration, pathologists can still have a hard time making a correct diagnosis. This potential variance can be the difference between a drug being approved and it failing the clinical trial.
How PathAI utilizes machine learning to power drug development