Routine tissue is cut at 3–5 µm, typically one cell thick, one section per slide, and one slide per block. Biopsy tissue is usually cut at 2–3 µm, a few sections per slide, and 2–3 slides per block. When stains are ordered, unstained slides are requested. Cut the unstained slides (at appropriate microns) according to the stain ordered or tissue type. Table 1 below lists some tissue types requiring tissue section thickness considerations:
Table 1. Tissue Types and Corresponding Section Thickness Requirements. | Tissue Types | Micron Requirement |
Brain and central nervous system (CNS) tissue | - 8–10 µm
- Requires much thicker sections to show neurons
|
| Tissue for amyloid diagnosis employing Congo red stain | |
| Renal (kidney) biopsies | - 2 µm to show glomerular basement membrabe
|
| Lymph nodes | |
Special sectioning protocols
Specific tissues have special cutting protocols, including:
- Levels: Most common for biopsies, 2–5 levels per block can be used to evaluate various tissue planes.
- Typically, one level equals 8–10 sections of tissue. However, each histotechnologist must use their judgment/discretion when sectioning levels.
- Levels can be collected initially or as a recut request.
- Block is faced, and one ribbon of 10 sections is cut. The first and last sections of the ribbon are taken for the first two levels, and the 8 sections in between are discarded.
- Another ribbon is cut, and the last sections are taken for the third level. The rest of the ribbon is discarded.
- Repeat until all levels requested are collected from a single block.
- Deepers: Common for skin biopsies. Used to seek out certain tissue elements, like cancer cells.
- A deeper section is collected, usually as a recut request.
- Once the tissue is faced and ribboned initially. It will be sectioned again to reveal tissue after 20–30 sections and collected again. A full ribbon is discarded between the collections.
- Serial sectioning: Common for biopsies, especially for diagnosing Hirschsprung's disease.
- Tissue is minimally faced to reveal the first few cells.
- Consecutive sections must be collected without losing any tissue sections in between ribbons.
- Up to 10 sections are placed on one slide.
- About 300–400 “snapshots” are collected to reveal the entire tissue.
- Very difficult and time-consuming.
