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 mm^2[1]
• AO with 10x eyepiece: 0.12 mm^2[1]
• Olympus with 10x eyepiece: 0.16 mm^2[1]
• Nikon Eclipse E400 with 10x eyepiece and 40x objective: 0.25mm^2[2]
• Leitz Ortholux: 0.27 mm^2[1]
• Leitz Diaplan: 0.31 mm^2[1]

Examples of usage

The area provides a reference unit, for example in reference ranges for urine tests.^[3]

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.^[4]

The following grading is part of classification of breast cancer:

Mitotic count per 10 high-power fields (HPFs)^[1]

Area per HPF					Score
0.096 mm2	0.12 mm2	0.16 mm2>	0.27 mm2	0.31 mm2
0-3	0-4	0-5	0-9	0-11	1
4-7	5-8	6-10	10-19	12-22	2
>7	>8	>10	>19	>22	3