Basic Principles of Stereology

Abstract

Stereology is often confused with morphometry, which is the commensuration of structure. The measurement of tissue elements on slides or photomicrographs disregarding their three-dimensional property is a kind of morphometry. A tailor who measures the customer for a suit is a practising morphometrist. Stereology, however, is the rigorous extrapolation from two- to three-dimensional space and a complex body based upon geometrical probability and mathematical methods that derive three-dimensional information from random sections or projections. Every section can be considered as a planar probe utilized to penetrate an aggregate structure. The resolution obtained will depend on section thickness and on the mode of observation. In biologic research the optimum resolution will be achieved by penetrating an aggregate with ultrathin sections and observing them using transmission electron microscopy. Quantitative relationships exist between the dimensions of cells or organelles and their profiles displayed on a section. This means that the aggregate of profiles on the planar probe or a unit area of it is reflecting quantitatively the aggregate of the corresponding structure in space or in a unit volume. This means that measurements obtained on sections can be described in terms of a structural dimension by stereological relationships. Stereological analysis of tissue and cells is based on several presuppositions. The individual tissue or cell component to be investigated must be (a) present in an adequate number; (b) unequivocally identifiable on the section; and (c) of similar size and shape at different locations within the tissue.