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.



Contacting the pathologist is recommended if a practitioner has concerns about a pathology report (e.g. has questions about the diagnosis, prefers clarification of an interpretation, or needs help with narrowing the differential diagnoses) or the report correlates poorly with the clinical findings. However, if information such as the sample source, patient history, and pertinent clinical abnormalities was not included with the original submission form, be sure this information is readily available when the pathologist is contacted. Proper communication is essential to a positive outcome.


Practitioners may be apprehensive about contacting pathologists. One concern is that pathologists are too busy to discuss a particular case. However, inquiries from practitioners are relatively common, and pathologists typically correspond with practitioners in a timely manner. Another concern is that practitioners may think pathologists perceive questions as a challenge to their interpretation. Pathologists are generally receptive to discussing their interpretation, other possible differential diagnoses, and any additional test results that may strengthen the confidence in the diagnosis.

Conversely, pathologists may contact practitioners about a challenging case or if they identify a potential problem. Pathologists may also seek additional information to solidify a diagnosis or narrow their list of differential diagnoses.

Practitioners and pathologists benefit from a good working relationship established through proper communication and cooperation when challenging cases arise.


Obtaining a second opinion is an option when a practitioner has concerns about a pathology report. However, before this option is elected, it is important to determine if the pathologist was provided an appropriate patient history, a sample source, and pertinent clinical findings. Contacting the pathologist before requesting a second opinion may resolve a case issue and alleviate concerns. Furthermore, the practitioner may find that the pathologist obtained a second opinion before completing the report, which is fairly common when dealing with challenging cases.

Another important factor to consider is why a second opinion is needed. If the interpretation does not correlate with the clinical findings, requesting a second opinion is reasonable. But when pathologists express concern that a sample is poorly representative of a lesion, obtaining a second opinion is unlikely to provide much additional information or result in a definitive diagnosis. For example, obtaining representative tissue samples can be particularly challenging with lesions involving bone or masses arising within the oral cavity (e.g. gingival or odontogenic tumors). It is not uncommon for core biopsies of bone masses to predominantly contain secondary reactive bone, with no clear evidence of the primary underlying lesion. With these types of cases, additional sample collection may be necessary to obtain a diagnosis.


Pathology reports often include a section containing comments about the case. Depending on the sample and information provided by the practitioner, the comments may be case-specific or relatively generic. In the absence of key information, when the sample quality is not ideal, or when faced with complicated cases, the pathologist may be hesitant to provide a definitive diagnosis or express a high degree of confidence in his or her interpretation. In these cases, it is common for the practitioner to receive a list of differential diagnoses and recommendations for other tests or procedures (e.g. histologic examination, special stains, serology, culture, molecular assays, or collection of additional tissue samples).


Below are several tips that may be useful in preventing common sample submission and interpretation problems.

Problem: Poor tissue exfoliation or low cellularity cytology samples

Avoid using small syringes (1 ml or 3 ml) and select a 20- to 25-ga needle. A 22-ga needle with a 5-ml or 6-ml syringe seems to work well in most situations.

Certain lesions may exfoliate poorly regardless of the technique used (e.g. mesenchymal neoplasms). Aspirates from lipomas are often of low cellularity when lipid material is lost from the slide during routine processing.

Aspiration of fluctuant areas of a mass can also be problematic, as many different lesions can be cystic. Cells from the cyst wall may not exfoliate in significant numbers into the fluid, and evaluation of fluid alone is unlikely to be diagnostic. A fluctuant or cystic area could also be due to tissue necrosis or secondary inflammation that might not be representative of the lesion. Consequently, aspiration or biopsy of the lesion wall (more solid area) is recommended.

Problem: Blood contamination of cytology samples

Some practitioners prefer to collect cytology samples by using an aspiration technique (e.g. 22-ga needle attached to a 5-ml syringe). For this method, the needle should be inserted into the mass or tissue and the plunger rapidly withdrawn once to develop negative pressure. Excessive withdrawal of the plunger will not result in a better sample but will increase the likelihood of blood contamination and cell rupture. This negative pressure is maintained while the needle is partially withdrawn and carefully redirected into several areas for aspiration. Redirection should be done carefully to avoid excessive tissue trauma and bleeding. The negative pressure is then gently released before fully removing the needle, to avoid loss of cells into the syringe. After removal, the needle is detached from the syringe, and air is drawn into the barrel. The needle is then reattached to the syringe, and the sample is expelled onto the slide. The sample is then prepared for staining using techniques discussed in the next section.

A sewing machine, or woodpecker, technique, which uses only the needle hub without syringe aspiration, is an excellent alternative to the aspiration technique described above. The needle is placed into the lesion followed by a controlled sewing machine motion for cell collection. The needle may be partially or fully withdrawn and redirected to sample additional areas of the lesion. The needle is then attached to an air-filled syringe, and the sample is expelled onto a slide for further preparation.

Keep in mind that certain lesions such as hemangiomas, hemangiosarcomas, thyroid tumors, and mast cell tumors are frequently associated with marked blood contamination because of the intrinsic vascular nature of the lesion.


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