Although it is rare, puppies and kittens can develop cancer.
The waiting room of a veterinary cancer specialist is pretty much a geriatric zone. The commonly treated cancers in adult dogs and cats include lymphoma, osteosarcoma and mast cell tumors. Research shows the average age of cats with lymphoma is 9 to 12 years and the average age of dogs with the same disease is 6 to 9 years. The numbers for osteosarcoma and mast cell tumors for older pets stack up similarly.
Just as I see in our companion animals, most human oncologists also consider human cancer to be largely a disease of middle-aged to older adults. However, according to the American Cancer Society, children can and do get cancer. The most common forms of the disease in children are leukemia, brain tumors, lymphoma and osteosarcoma. There are also a group of malignant (cancerous) tumors in children that arise from immature cells. Rare in adult humans, these tumors have the ominous suffix “blastoma” at the end of their name: neuroblastoma (involving the nervous system), nephroblastoma (involving the kidney) and retinoblastoma (involving the eyes). One has to wonder, if children can get cancer, then what about puppies and kittens? Are there signs we should be on the lookout for in our pets — even the youngest ones?
What We Know About Puppy and Kitten Cancers
Not much is written about tumors in pediatric dogs and cats (those less than 1 year of age). My big, fat veterinary oncology textbook does not have a chapter on the subject, nor is it listed in the index. Using a search engine for medical information, I found very little on the topic of pediatric dog and cat tumors. As a veterinary cancer specialist, I see only a select few pediatric tumors since a primary-care veterinarian handles the most common benign tumors (benign meaning those that cannot spread) and the rare ones are, well, rare. But in an effort to put our headline question into some context for pet owners, I will summarize the information I found, as well as my experience as a veterinary oncologist, below.
3-2-1 – Good Numbers to Keep in Mind
Here’s one thing you definitely should know as the owner of a young pet. Puppies and kittens receive a series of vaccinations intended to protect them from serious infectious diseases like distemper, rabies and parvovirus. Vaccinations can cause the formation of a lump at the site of injection. These lumps can form because vaccination turns the immune system on and a huge assembly of immune cells collects at the vaccination site. Normally, the cells dissipate over a week or so. But veterinarians and pet families should follow the 3-2-1 rule when it comes to addressing post-vaccination lumps: If the lump has been present for more than three months, is greater than 2 cm (1 inch) in diameter or is still growing one month after vaccination, the lump should be removed and biopsied. Occasionally, these lumps can become malignant and early removal is key to successful treatment. I see a handful of injection-site tumors each year.
Warts: Trouble but Not Tumors
Although not a malignancy, growths known as papillomas or warts resemble a tiny cauliflower tumor on the skin. An infection with a virus is the cause of multiple types of papillomas in young dogs. Here in New York City I see a case of “puppy warts” every couple of years. If the infection is severe, literally hundreds of warts can form around the mouth and face of an infected dog. Despite the widespread distribution of warts, your puppy’s maturing immune system will ultimately contain the infection and the warts will regress without medical intervention. Cats have their own papilloma virus, which is reportedly extremely rare, and I have never seen a feline patient with papilloma-virus-induced warts.
Common, but Typically Benign
The most common tumor identified in a British study of biopsies in pediatric dogs was the cutaneous histiocytoma. When I see a young dog with a skin mass resembling a raspberry or strawberry on the skin, I immediately think histiocytoma, in part because these benign tumors are so common. Occasionally I see histiocytomas in mature dogs as well. The British study showed nearly 90 percent of tumors biopsied in pediatric canine patients were histiocytomas. Like warts, histiocytomas will regress spontaneously, but if they are messy and bleeding or occur in a location like the paw, which is painful, veterinarians often remove these tumors surgically. The British study also identified a small number of malignant tumors such as mast cell tumors, lymphoma and osteosarcoma in puppies. The malignant “blastoma” type tumors seen in children thankfully appear to be extremely rare in puppies based on the results of the British study. In comparison, in adult dogs, the most common type of cancer varies geographically. In Europe, for example, breast cancer dominates, while in the United States, lymphoma and hemangiosarcoma are more frequently diagnosed.
Of Concern for Kittens
The same group of veterinary researchers in England who did the puppy study also conducted a study of biopsies in kittens. However, the results were vastly different. In the dog study, nearly 50 percent of the total number of biopsies submitted to the lab from puppies were tumors, either benign or malignant, but in the cat study, only 6 percent of the total number of biopsies submitted to the lab were tumors. The researchers do not specify the results of the other 94 percent of biopsies, but I would suspect they found ringworm, abscesses and post-vaccination inflammation. But the 6 percent in this study was too high for me since it found that nearly all the tumors diagnosed in kittens as opposed to puppies were malignant. As in adult cats, the most common tumor diagnosed via biopsy in kittens is lymphoma, followed by mast cell tumors and then a group of tumors known as carcinomas. Benign tumors ranked low, at the bottom of the list. Similar to the dog, malignant tumors arising from immature cells (those ending in “blastoma” as seen in children) were extremely rare in kittens based on the results of the feline survey.
Pet Cancer Awareness
Since even the youngest furry family member can develop cancer, all pet families should familiarize themselves with vetstreet’s 10 Warning Signs of Cancer in Pets. Although relatively uncommon, certain pediatric pet tumors can be malignant so you should never hesitate to bring any lump on your pet to your veterinarian’s attention regardless of the age of your pet.