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[1]
AO with 10x eyepiece: 0.12 mm²[1]
Olympus with 10x eyepiece: 0.16 mm²[1]
Nikon Eclipse E400 with 10x eyepiece and 40x objective: 0.25mm²[2]
Leitz Ortholux: 0.27 mm²[1]
Leitz Diaplan: 0.31 mm²[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	Score
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

References

Unless otherwise specified in list/table, then reference is: "Infiltrating Ductal Carcinoma of the Breast (Carcinoma of No Special Type)". Stanford University School of Medicine. Retrieved 2019-10-02.
Mikael Häggström (2020-01-29). "Neuroendocrine tumors of the midgut". Patholines.org.
Normal Reference Range Table Archived 2011-12-25 at the Wayback Machine from the University of Texas Southwestern Medical Center. Used in interactive case study companion to pathologic basis of disease.
Robbins Basic Pathology, 9e pg 792

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[stanford-1] Unless otherwise specified in list/table, then reference is: "Infiltrating Ductal Carcinoma of the Breast (Carcinoma of No Special Type)". Stanford University School of Medicine. Retrieved 2019-10-02.

[2] Mikael Häggström (2020-01-29). "Neuroendocrine tumors of the midgut". Patholines.org.

[southwest-3] Normal Reference Range Table Archived 2011-12-25 at the Wayback Machine from the University of Texas Southwestern Medical Center. Used in interactive case study companion to pathologic basis of disease.

[4] Robbins Basic Pathology, 9e pg 792