HPF
To assess the frequency of the relevant phenomenon, usually mitoses or cells, in the studied histopathological image, frequency in the fields of view of the microscope at the highest magnification is usually used . In order to eliminate the influence of random fluctuations, it may be recommended to evaluate more fields of view, e.g. 10. The choice of magnification of the objective (40x) and the eyepiece (10x) is usually the same on all common microscopes, so the assumed total magnification of 400x is usually achievable. The design of the eyepiece can affect the doctor's field of view, so 1 HPF can have an area of 0.1-0.4 mm². Similarly, the meaning of HPF may disappear if the eyepiece is replaced by a camera, or a virtual specimen is used directly. Therefore, in the recommendations with histopathological diagnostic criteria, next to the number of HPFs, a metrically specified area to be analyzed appears.
