How to get better pathology results - Veterinary Medicine
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How to get better pathology results
Find answers to your questions about submitting samples for cytologic and histologic examinations and communicating with pathologists—plus, tips for avoiding common mistakes.



Nondiagnostic cytology samples are commonly submitted for evaluation. This complication can delay patient treatment or prevent the practitioner from moving forward with additional diagnostics or procedures. Client frustration can occur over the cost of the test and time spent awaiting results, even if forewarned the procedure may be inconclusive.

When surgical biopsy samples are being submitted, practitioners are somewhat limited in assessing the sample quality. However, when samples are sent for cytologic evaluation, practitioners should stain at least one slide and examine it on low magnification (10X objective) to avoid submitting nondiagnostic samples.

1. A lymph node aspirate from a dog containing numerous bare nuclei from ruptured cells, with abundant purple, streaming nuclear material in the background (Wright's stain, 20X objective). (Photo courtesy of Dr. Rebeccah Urbiztondo.)
Common reasons for cytology samples being deemed nondiagnostic are marked blood contamination, a large number of ruptured cells (Figure 1), and low cellularity. Practitioners can often recognize these problems on low magnification and obtain another sample of the lesion. If further evaluation of sample quality is necessary, a temporary coverslip (without adhesive) can be placed on the slide followed by examination with the 40X objective.

Another potential problem that can result in a nondiagnostic sample is submission of slides that are understained or not properly fixed, which can make interpretation difficult or impossible. Slides that are not fixed adequately often cannot be restained and lack nuclear detail. For rapid Romanowsky-type stains (e.g. Diff-Quik—Dade Behring, Hema-Diff—Statlab), the recommended protocol for each product can be used as a general guideline. However, the time required for proper fixation and staining depends on the thickness of the preparation. In general, more time is required for highly cellular or proteinaceous specimens, such as liver aspirates or synovial fluid.

Well-stained nucleated cells should have dark-pink to purple nuclear chromatin, whereas nuclei from poorly stained cells may appear very pale blue or light pink. While understained slides can undergo additional staining at the laboratory, this may be of limited use for samples previously evaluated on oil magnification (100X objective). Immersion oil can interfere with additional staining, potentially rendering the sample nondiagnostic.

For specimens submitted for cytologic examination, submit multiple slides per site (three or four is generally sufficient), which may include stained and unstained specimens. Submitting only one or two slides, particularly if these have been previously stained, may limit cytologic evaluation depending on the sample quality.


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