Submitting Samples for Histopathology

We accept specimens submitted in fixative containers or tissue cassettes. We encourage specimen submissions in tissue cassettes, as you know your samples best and can ensure that areas of interest are captured. There is also a cost-saving if you submit in cassettes.

• Standard practice is to place the surface of interest down in the cassette, the tissue surface placed down in the cassette is then the first to be sectioned.
• To prevent loss of small tissues during processing, use a biopsy cassette, biopsy bag, or wrap the specimen in filter paper in the cassette.
• While multiple tissues may be placed in the same cassette, there are a few important considerations to ensure high quality.
• Only tissues of the same consistency can be combined into the same cassette. For instance, liver and kidney have a similar consistency, but not liver and brain. Bones require decalcification and should never be combined with other tissue types.
• Tissues must be cut thin before placing them in a cassette. This may require further trimming after they are fully fixed. The rule of thumb is that tissues in a cassette be no thicker than a nickel (0.2-0.5 cm).Tissues that are too thick or overcrowded in the cassette will not yield good results, as the specimens will not adequately fix, infiltrate with paraffin, section, or stain.
• If your submission contains tissues that vary significantly in size (i.e., whole organs vs. biopsies) or consistency (i.e., soft tissues vs. bone or soft tissues vs. brain), sort similar cassettes into separate containers.
• Label cassettes clearly and refrain from excessively long specimen IDs to ensures correct slide labeling.
• Use only hard pencil (or specially purchased histology markers) when labeling cassettes. Never use pen, Sharpie marker, or scientific freezer-safe markers, as solvents used in tissue processing can dissolve this ink!
• For your convenience we offer cassette printing services, as does the Animal Studies Core on the opposite end of campus.  https://www.med.unc.edu/ascore/

Tissue embedding is the careful orientation of processed tissues into a mold with paraffin wax, which provides a stabilization medium for microtome sectioning.

• Our standard is to place one specimen per tissue block.
• Additional tissues may be embedded together in the same block, size permitting. A maximum of 4 tissues can be embedded per block, although additional charges may incur.
• If it is critical to capture a specific plane within a tissue, placing multiple tissues in the same block is not advised.
• Please list any special embedding requests on the submission form.