Special stains for lipids
In histology, the term "lipids" corresponds to fats and assimilated substances as well as to substances containing fats. All of these substances include, for example, triglycerides, fatty acids, lipoproteins and glycolipids.
It is quite difficult to visualize the lipids in histology because they are dissolved in the solvents used for the preparation of the tissues. This means that the lipids can disappear from the tissue during the preparation and especially when it comes to paraffin sections. It is for this reason that frozen sections are more commonly used for lipid visualization. However, not all lipids are eliminated by solvents. This is the case of lipids that bind to other molecules such as lipoproteins, lipofuschins and myelin. On the contrary, triglycerides are always removed by the solvents during the preparation of paraffin tissues.
The cell membranes are composed of a large amount of lipoproteins, and although these are not dissolved by the solvents, it is very difficult to demonstrate them by conventional methods of lipid staining.