by Kim Freeman, DVM, DACVIM (Oncology) | John Wooldridge DVM, DACVS

Medical oncologists spend a lot of time looking at histopathology reports. These reports can be full of large, difficult-to-pronounce words describing the microscopic appearance of cell and nuclear morphology. Often these words seem superfluous and generally uninteresting and unnecessary. But, to an oncologist, they are truly amazing words! Anisokaryosis, anisocytosis, karyomegaly, nucleolar morphology, mitotic index.
What does a biopsy/ histopathology tell us?
We look carefully at all of this information and try to create an image in our head of what the pathologist is seeing. How aggressive, infiltrative or invasive is this tumor? What is it doing to the surrounding normal tissues? What is its proliferative index? All of this is helpful in explaining a diagnosis and tumor behavior. All of this is typically included in a microscopic description of a pathology report.
It may cost a little more to get this information, but it is worth it! As is sending out the mass for pathology in general.
What are margins?
Another very important part of the pathology report is the description of surgical margins. For some reason, some pathologists do not well document this information on their reports, and there is little consistency between different pathologists as to how they actually describe and quantify margins. So, it becomes our job as the dutiful clinician to call our pathologist and kindly request that they give us a detailed report of surgical margins. Now, this information should be taken in context with the surgical approach, because we all know that tissue starts to contract as soon as an incision is made and then shrinks even more once placed in formalin. However, there are still important things we can glean from the pathology report of surgical margins. Please note, if a pathologist says something is “completely excised,” but does not tell you the margin of excision, ask for more information! It would be very helpful if pathologists could add qualifiers such as “narrowly” excised or “widely” excised to bring to our attention a heightened awareness to the importance of margins. It is quite common to see that a pathologist will call something completely excised, even if the margin of excision is less than 1 mm! This can make all our lives quite difficult! Partly because it is amazing that they can measure something that is less than 0.2 mm and partly because they often inadvertently convey that a tumor might be well controlled with such a narrow excision. While, this might be true, since a complete, though incredibly narrow, excision of a benign tumor is totally fine. It might even be fine for a low grade malignancy, though I would always caution that malignant tumors should truly be widely excised to guarantee that it won’t recur. However, 1-2mm surgical margins are not adequate for most of the common malignancies we all see, such as a soft tissue sarcoma, hemangiosarcoma, higher grade mast cell tumors, malignant melanoma, etc. This type of “narrow” excision, even if the pathologist says “complete”, is NOT enough to confidently advise that the tumor is completely and cleanly excised in most situations. Understand the difference between “narrow” but “complete” excision. It means that we cannot promise that the tumor won’t grow back.
Take photos!
To even further improve your surgical oncology skills, we encourage everyone to embrace digital photography as part of your medical record keeping. Pre-operative photos and intraoperative photos can be quite helpful in planning adjunctive therapy, and in helping the medical oncologist understand exactly what this mass looked like before any treatment. From a surgical oncology perspective, the deep margins should ideally include the underlying fascial plane. This is a natural barrier to disease in most tumors, and is an important part of tumor control. It is helpful to the oncologist to know whether this tissue was removed during surgery or not.
Consider a consultation with a specialists:
It is quite common that we can see referrals after incomplete excisions of various tumors, especially in challenging anatomic areas like the distal limbs, neck, face, and perineum. Often, the surgical planning in these areas is complicated by concerns about closure of the area, or local anatomy, and then the actual excision is compromised. We would strongly recommend early referral in any situation where margins will be challenging, or where incomplete margins will make follow-up treatment more complex based on the pre-operative tumor diagnosis. In addition, if your vet is uncomfortable taking the necessary tissue margins during surgery, including the fascial plane underlying the tumor, consider referral to a surgeon. It often avoids the need for second surgeries of incompletely or narrowly excised tumors.
As a team effort to make sure we are doing all we can in the fight against cancer,If you have questions about preoperative cytology, tumor diagnosis, or surgical plan, consult with a medical oncologist and/or surgeon. In this long run, this improves all of our patient care and outcomes.