Cancer? Not So Fast—For Some Dogs, it May be a New, Benign Syndrome

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While scientists at Colorado State University were continuing their research into B-cell chronic lymphocytic leukemia (BCLL) in English bulldogs, they uncovered something unexpected—despite presenting with common clinical indications, some dogs did not actually have the cancer. Instead, they found that the common cancer is easily mistaken for a never-before-described benign syndrome the team named polyclonal B‐cell lymphocytosis.

"This could save some dogs from being misdiagnosed, treated for cancer or even euthanized when they shouldn't be," said Anne Avery, professor of immunology and pathology at Colorado State University. "The dogs may look to their veterinarians like they have leukemia, based on original diagnostics, but they don't actually have cancer."

As a small-breed dog, English bulldogs have an increased risk of developing BCLL. Even with that knowledge, during previous research Avery and her team noted that English bulldogs with the cancer presented uniquely compared with other breeds, including small ones also considered high-risk. According to the researchers, English bulldogs were significantly younger when they presented with the cancer, had increased frequency of hyperglobulinemia and expressed their B-cells differently and at a decreased rate than mixed breed dogs.

To investigate further, the team dipped into their database of 195 blood samples from English bulldogs, focusing on 84 cases that showed increased numbers of B-cells. Using flow cytometry, the researchers examined the numbers and types of antibodies the dogs produced. Based on the results, as well as an assay test that showed the B-cells did not arise from a single, cancerous cell, the team concluded that 70 percent (58 of 83) of the dogs did not have cancer.

Instead, the 70 percent that presented with most of the clinical signs of BCLL—but without clonal immunoglobulin (IG) arrangements—had polyclonal B‐cell lymphocytosis, or non-malignant B‐cell expansion.

The dogs diagnosed with polyclonal B‐cell lymphocytosis tended to be just a year or two old, and three-quarters were male. Additionally, more than half presented with hyperglobulinemia, as well as an enlarged spleen.

In their paper, published in the Journal of Veterinary Internal Medicine, Avery and team hypothesize that the newly described syndrome begins as a benign condition, but does possess the potential for malignant transformation over time.

"This important finding demonstrates that we shouldn't assume that a high B-cell count always indicates cancer in English bulldogs," said Janet Patterson-Kane, Morris Animal Foundation Chief Scientific Officer. "This is very important information for veterinarians who may initially see these patients in their clinic."

The study authors believe the syndrome “almost certainly” has a genetic basis, although more research is needed on that front. Currently, the team is looking for evidence of the syndrome in other breeds—although they hypothesize it is specific to English bulldogs. Next, they intend to search for the genetic mutation that leads to the syndrome, as well as continue to monitor the dogs for a longer period of time to fully understand the health ramifications—if any—of persistently high B-cell numbers.

Photo: Tootsie was one of 84 English bulldogs that supplied blood that helped researchers discover a non-cancerous syndrome, called polyclonal B-cell lymphocytosis, that could be mistaken for a common cancer. Credit: Colorado State University