Oncology: An ounce of surgical planning worth a pound of long-term treatment - DVM
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Oncology: An ounce of surgical planning worth a pound of long-term treatment


DVM360 MAGAZINE


Saving money by not obtaining a microscopic description is also discouraged because there can be valuable information in the description regarding the potential behavior of a tumor. A full history should be provided to the pathologist to help correlate the diagnosis with the clinical picture. One of the most common complaints from pathologists is that they do not receive any history or have an incomplete history that hinders their ability to provide an accurate report.

As a rule, the entire tumor should be submitted to the pathologist, because tumors are heterogeneous in nature. Small samples may not be representative of the entire specimen. Submission of a portion of a tumor that contains only necrosis or inflammation may lead to the misdiagnosis of a benign lesion.

Different regions of a tumor can have more malignant features that can be important to identify because the expected behavior of a tumor would be based on the most malignant features.

In most cases, pathology labs provide clinics only with small specimen jars to submission samples in. The lab may be able to provide bigger containers for larger specimens, but it is possible to use other sealable containers, such as Tupperware for these samples. Formalin cannot penetrate into large samples but fixation can be improved by making partial slices into the tumor at 1-in. intervals to allow formalin to penetrate into the specimen. Larger samples can be fixed for 24 hours in formalin and then transported to the lab wrapped in formalin-soaked paper towels in a sealed container.

Submission of only a portion of the tumor compromises margin evaluation. If the margins cannot be determined due to an incomplete submission, it may be necessary to recommend further local therapy that can result in higher costs for the owner as well as additional morbidity for the patient.

If possible, the margins should be marked for the pathologist so that it can be determined which margin (i.e., deep or lateral) is incomplete or narrow. Methods of marking the margins can be simple (India ink) or more complex (5-dye system) depending on the situation. Knowing which margin is narrow or incomplete can help determine if a re-excision would provide an adequate margin.

When a pathologist evaluates the margins, four or five representative margins typically are evaluated (i.e. lateral, medial, cranial, caudal and deep). Note that tumors are not spherical so that the actual margins can vary depending on which area is sampled. Margins are often reported as incomplete, narrow, wide or radical. Pathologists can also "quantify" the margins (i.e. 1 mm or 1 cm) to better help make treatment decisions. A tumor excised with a 1-mm margin may be reported as completely excised but likely requires additional treatment due to the narrowness of the margin.

When determining if a margin is adequate, consider the size of the tumor and the tumor type. Reported margins can be slightly underestimated as tissue has the tendency to shrink once it is placed in formalin.

Discussion of grading

Several tumors have accepted grading schemes that allow the pathologist to assign a grade to the tumor (i.e. mast-cell tumors, soft-tissue sarcomas). Further treatment may be recommended for high-grade tumors. Features that tend to be most important in determining the degree of malignancy include mitotic index, degree of differentiation, degree of necrosis and presence or absence of lymphatic and vascular invasion. Even for those tumors that do not have an accepted grading scheme, it may be possible to predict the behavior of a tumor based on evaluation of these features.

At some point you may be faced with a diagnosis that does not fit the clinical picture. It is up to you to question these cases and look for additional information. The first step usually is to speak with the pathologist about the case to see if the discrepancy can be resolved. If there are still unanswered questions, then having the biopsy reviewed by a different pathologist (or several), requesting special stains or immunohistochemistry (IHC) and/or obtaining additional biopsies, may be indicated.


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Source: DVM360 MAGAZINE,
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