This section briefly addresses how specimens are handled after collection, focusing on the types of samples found in the JPC repository. Figure 2-1 shows the relationship between the various materials collected and their forms of preservation for pathologic analysis.
The pathology workflow for tissues comprises collection or excision from the patient; visual examination of the macroscopic specimen (called a gross specimen); initial stabilization; transfer to a laboratory; selection of material from the gross specimen for further analysis; fixation; further visual examination; histopathologic, biochemical, or molecular analyses; and storage.
After collection or excision and any initial diagnostic evaluation, specimens are typically either frozen or chemically stabilized for transport. The essential processing steps for laboratory preparation of samples that are not maintained in a frozen state are summarized below.
Fixation. Fixative solutions stabilize tissue structure and biochemical constituents by coagulating (cross-linking, denaturing, and precipitating) proteins and thereby prevent cellular hydrolytic enzymes, which are released when cells die, from degrading tissue components and rendering tissues inadequate for microscopy. Fixation also immobilizes fats and carbohydrates, reduces or eliminates enzymatic and immunologic reactivity,
FIGURE 2-1 Relationship between pathologic materials collected and form in which they are preserved for analysis.