Manipulate Information and Courses from MediaLab, Inc.

Many histologists use forceps and other tools to help them manipulate and position tissue specimens in the desired arrangement. Histologists often have individual preferences for the size and shape of forceps they use. It is recommended that all types of forceps be wiped well between specimens to prevent carry-over contamination. The use of forceps without "teeth" or small grooves at the tip will also help in preventing carry-over. Tissue tampers or stamper can be used to apply pressure evenly on the specimen to help flatten it so that it will harden in one flat plane as the block solidifies. It is essential to make specimens as flat a possible in relationship to the block face for a single, representative section of the entire specimen to be obtained. Forceps and other tools used to manipulate tissue during orientation must be kept warm so that tissue fragments do not adhere to tools as the paraffin on them will begin to solidify on their the surface if they are too cool. Small warming wells are found in most embedding units for the purpose of keeping tools at the necessary temperatures. These wells should be cleaned as frequently as any tools used during embedding, as they can harbor small tissue fragments that can then be transferred to adjacent specimens.

Histologists must practice to be able to rapidly identify and orient specimens during paraffin embedding. Taking too long to manipulate and position the specimen may cause more than one layer of solidified paraffin to form when molten paraffin is added to paraffin that has solidified in the bottom of the base mold. These separate layers may pull apart during microtomy or storage. Pieces of all types should be placed with intention, in one plane, and not just randomly in the block face. Careless positioning will make it very unlikely that a single representative section can be easily obtained.Correct by re-embedding, any gross defects such as cracks or air bubbles. Observe the specimen for processing issues, such as poor fixation, dehydration, or infiltration. A "white-ish" appearing or "mushy" texture due to inadequate dehydration in a processed tissue block is most likely in need of reprocessing. Submit this block for reprocessing prior to embedding; it is much easier to take the specimen back through these steps for correction now than to work backward from the final cut block.Document and correct labeling discrepancies, illegible blocks, or incompleteness of cases during embedding, rather than "passing" these problems on to the microtomy step.

Coverslip smears are made on 22 x 22 mm coverslips using a technique similar to the pull prep method. If done correctly, both coverslips will have quality smears that will appear similar to a thumb print. To create a coverslip smear preparation, a coverslip is picked up by the corner and the point is held between the thumb and forefinger in one hand. The other hand uses a capillary pipette to transfer a small drop of concentrated bone marrow on to the center of the coverslip. The capillary pipette is put down and a second coverslip is placed over the first to form a star shape. When the marrow has spread almost to the edges, the coverslips are slid apart using the protruding corners/points of the star. The motion is a parallel slide with no pushing or rotation of the wrist as the coverslips are slid apart.Making smears on coverslips requires manual dexterity. Not only does the laboratory professional need to be proficient in the use of capillary tubes to pipette bone marrow, he/she must also be able to manipulate fragile coverslips without breakage. Staining also requires modified/adapted methods.A 22x22 mm coverslip can be glued to a standard slide after staining to provide easy evaluation. Since only a minimal amount of bone marrow is needed, many smears can be made from a small bone marrow sample. Another advantage is the small amount of storage space required. Three dozen coverslips will easily fit in an envelope and would take considerably less storage space compared to the same number of regular slides.