Treatment of Canine Lymphoma
Dear OncoLink "Ask the Experts,"
I've been trying to gather as much information as possible on treatment of canine lymphoma. I'm wondering if there are recommendations from oncologists for whole gland biopsy vs. needle aspirates. The two vets that I use in the same practice have conflicting opinions and I've been unable to find anything written about it. I would appreciate any guidance you can give me to find out more about this.
Lili Duda, VMD, Editor of the OncoLink Veterinary Oncology Section, responds:
This is an excellent question, and comes up fairly often—which means that there is no right or wrong answer and it is a matter of clinical judgment and past experience.
Needle aspirates look at a very small sample of cells that are "sucked" out of the lymph node and smeared onto a slide. The cell structure can be evaluated, but nothing can be said about the structure, or "architecture" of the entire lymph node. Clinical pathologists (cytologists) are the specialists trained to look at needle aspirate slides.
A whole lymph node biopsy provides much more information in that the distribution and overall numbers of cancerous cells can be evaluated, and many more cells overall can be evaluated. Surgical pathologists (histopathologists) are the specialists who look at these slides. In general, cytologists are not histopathologists (and vice versa) although individuals might be trained in both specialties.
In human medicine the distribution of lymphoma throughout a node is important for prognostic and therapeutic reasons. In veterinary medicine, while this information is important for academic reasons, it doesn't really make that much therapeutic difference. At VHUP, where we have an excellent cytologist, we go by her recommendation. If she is willing to call something definitively lymphoma on an aspirate, we will use that as definitive diagnosis. However, if she says "probable" or "possible" lymphoma (and certainly if she says a biopsy is needed for diagnosis) we will go ahead and do the biopsy.
An intermediate option is what is called a "Tru-Cut" biopsy which is a small core of node, that provides more tissue than a needle aspirate, but much less than a whole node surgical biopsy. The advantage is that a Tru-Cut can be done with just a local anesthetic in most cases.