 Universal guidelines for the management of cancer patients are difficult to define. Clearly, every tumor, every situation, every patient is different. But let’s try to define five general rules anyway.
Step 1  | | A nerve sheath tumor in a 10-year-old Sheltie. | The first challenge is to suspect or recognize cancer. It may seem straightforward with a skin mass, but it can be much more challenging in the intestine or the bladder. Confirming the suspicion is the next step, and it usually involves a fine needle aspirate (FNA) or a biopsy. Let’s simplify and only consider skin masses. There are two main FNA techniques: aspiration and trephination. The traditional aspiration technique requires a needle and a syringe. The needle is introduced into the tumor in various directions, while negative pressure is applied to the syringe. “The microtrauma created may cause bleeding, which will lead to hemodilution of the sample,” xplains Ken Mero, DVM, Ph.D., a pathologist at Histology of Stone Ridge in Stone Ridge, N.Y. Another method is the trephination technique, which doesn’t involve negative pressure and reduces the risk of hemodilution. Tiny cores of the mass are harvested without using negative pressure, which may allow a higher cellular yield by avoiding hemodilution. Incisional biopsy techniques include Tru-Cut, wedge or punch biopsy. Excisional biopsy is a fancy synonym for “trying to remove a tumor entirely,” i.e. with clean margins. The results of an FNA and a biopsy have two important differences. An FNA sometimes will provide an actual diagnosis (e.g. mast cell tumor) and often will include several rule-outs. A good biopsy will typically provide a definite diagnosis and the grade of the tumor, when applicable. In addition, the pathologist can study the architecture of the sample and visualize cells in their original microstructure. Last but not least, an excisional biopsy helps with assessing the surgical margins—“clean” or “dirty.” “Grading is a complex and subjective endeavor. Grading a tumor involves describing how differentiated or aggressive it is. The pathologist will describe a tumor as being low, moderate or high grade. Another description is a poorly, moderately or highly differentiated tumor,” Dr. Mero explains. A mast cell tumor is somewhat easier to grade—1, 2 or 3, with 3 being the most aggressive. For a variety of medical or financial reasons, an FNA or an incisional biopsy may not be performed. Step 2  | | A mammary spindle cell sarcoma in an 11-year-old Maltese. | The second step is staging a tumor, which helps specify whether it has metastasized. The tests involved can include: - Simple palpation, such as of the peripheral lymph nodes.
- Radiographs—thoracic or abdominal.
- Ultrasound—thoracic or abdominal.
- CAT scanner, most often of the thorax.MRI, possibly adequate for the abdomen but usually not for the thorax because of the constant motion of the heart and lungs...
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