High-power field

A high-power field (HPF), when used in relation to microscopy, references the field of view under the maximum magnification power of the objective being used. Often, this represents a 400-fold magnification when referenced in scientific papers.

Area
Area per high-power field for some microscope types:
 * Olympus BX50, BX40 or BH2 or AO: 0.096 mm2
 * AO with 10x eyepiece: 0.12 mm2
 * Olympus with 10x eyepiece: 0.16 mm2
 * Nikon Eclipse E400 with 10x eyepiece and 40x objective: 0.25mm2
 * Leitz Ortholux: 0.27 mm2
 * Leitz Diaplan: 0.31 mm2

Examples of usage
The area provides a reference unit, for example in reference ranges for urine tests.

Used for grading of soft tissue tumors: Grading, usually on a scale of I to III, is based on the degree of differentiation, the average number of mitoses per high-power field, cellularity, pleomorphism, and an estimate of the extent of necrosis (presumably a reflection of rate of growth). Mitotic counts and necrosis are the most important predictors.

The following grading is part of classification of breast cancer: