Tissue processing involves dehydration of the specimen to allow infiltration of the tissue with paraffin. The tissue is then embedded in a paraffin block, which mechanically stabilizes the tissue, enabling it to be cut into very thin sections.
The organic solvents used in tissue processing—for example, ethanol and xylene—dissolve lipids and may dissolve some synthetic materials. Routine processing usually dissolves intraocular lenses made of acrylic or silicone but does not dissolve sutures made of silk, nylon, or other synthetic materials.
Figure 2-3 Preparation of an intraocular tumor enucleation specimen. A, Transillumination shows blockage of light due to an intraocular tumor. B, The shadow is traced with a marking pencil. C, The opened eye shows the intraocular tumor that was demonstrated by transillumination. D, The paraffin-embedded eye shows the intraocular tumor. E, The hematoxylin-eosin (H&E)–stained section shows that the maximum dimension of the tumor, demonstrated by transillumination grossly, is in the center of the section, which also includes the pupil–optic nerve (PO) section.
(Part A courtesy of Nasreen A. Syed, MD; part B courtesy of Hans E. Grossniklaus, MD.)
The processing of a routine specimen usually takes a day. Techniques for the rapid processing of special surgical pathology material are generally reserved for small biopsy specimens that require urgent handling. Rapid processing usually results in inferior tissue preparations and therefore should not be requested routinely. Surgeons should communicate directly with their pathologists about the availability and shortcomings of these techniques.
Figure 2-4 Gross dissection of a globe. A, The goal of sectioning is to obtain a PO section that contains the maximum area of interest. B, Two caps, or calottes, are removed to obtain a PO section. C, The first cut is generally performed from posterior to anterior. D, The second cut yields the PO section.
(Illustration by Christine Gralapp.)
Excerpted from BCSC 2020-2021 series: Section 4 - Ophthalmic Pathology and Intraocular Tumors. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.