  This paper discusses some overlooked challenges faced when working with
machine learning models for histopathology and presents a novel opportunity to
support "Learning Health Systems" with them. Initially, the authors elaborate
on these challenges after separating them according to their mitigation
strategies: those that need innovative approaches, time, or future
technological capabilities and those that require a conceptual reappraisal from
a critical perspective. Then, a novel opportunity to support "Learning Health
Systems" by integrating hidden information extracted by ML models from
digitalized histopathology slides with other healthcare big data is presented.
