Slides preparation for the on-site cytology evaluation is an easy and quick technique. It is not part of the teaching curriculum of all interventional pulmonology training programs. The acquisition of basic cytology skills could be incorporated during training, as it might be helpful when there is no adequate support staff.
In terms of slide preparation, after the specimen is obtained, the tip of the needle is held with the beveled end facing and oriented downward to expel a small drop onto the slide. A second slide is used as a shield and held at an angle to prevent expelled material from getting splayed.
The smear is made by placing the second clean slide directly over the specimen, which is gently pressed to allow even spread. As it starts to spread, pull gently the slides apart with a one fluid motion. You will end up having two slides containing smear.
One slide can be immediately fixed in the alcohol solution, the other is allowed to air-dry at room temperature for rapid staining, the rest of the specimen can be expelled directly into a preservative solution for histologic evaluation.
Specimen Collection:
There are numerous liquid medias used for collecting needle aspirates, the choice of the solution depends on the type of the investigation needed. For example: aspirated material expelled directly into a sterile normal saline container provides flexibility for microbiology testing, the hanks solution has a physiologic pH and is used to maintain the cells in a viable state, the RPMI is used for flow cytometry, it also keeps the cell viable and it is used when the clinical suspicion is that of lymphoma, formalin is a widely available fixative solution and comes in a prefilled container, alcohol also serves as a fixative and can come in a very useful prefilled 4-slide jars, this can be helpful when onsite staining is not an option; slides can be smeared, fixed in alcohol, and transported to the lab for staining and processing.
The diff quick staining method is one of the most commonly used worldwide, it is a quick method, with a very short staining time, and uses three different solutions: alcohol, eosin and methylene blue solution.
The slides are either air dried or wet fixed in alcohol, the slide must be fully air-dried before going briefly into the first solution that is methanol,
the slide then is removed from there, held vertically and gently tapped on a dry paper to remove the extra liquid, then it is moved into eosin for few seconds,
once again, the excess liquid is removed and the slide is dipped into methylene bleu for an additional few seconds.
For wet slides that were immediately placed in alcohol, they are taken to the lab to be stained with either H&E or Papanicolaou.
The Diff-quick method stains the nucleus in blue to purple color, the cytoplasmic staining is more variable, red or pink for red blood cells, light blue for macrophages and lymphocytes, it often stains cilia pink, which is helpful for identifying bronchial cells.
Adenocarcinoma
Cell blocks increase the diagnostic yield and can be archived for future diagnostic and research purposes, while allowing the original smears to be preserved. A cell block is a technique that converts a cytological aspirate into a histological specimen. Different approaches have been described. The HistoGel method is shown here, and it involves several steps.
The specimen is centrifuged and the supernatant is poured off.
Liquefied HistoGel is added to the tube allowing the mix to solidify and form a solid concentrated cell button.
It is then wrapped in filter paper and placed in a histology cassette. The block is the end result after processing when the button has been embedded in paraffin. The specimen is then processed routinely by the histopathology lab. Immunohistochemistry stain and molecular studies are performed preferably using the cell block, but can also be done from the smears if necessary.
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