October 25, 2026, 11:06 am | Read time: 5 minutes
While petting your four-legged friend, you suddenly notice it: Is that a lump? It can have many causes, and some are harmless. However, it might be a malignant tumor. As dogs and cats live longer today, more of them are developing cancer. A diagnosis doesn’t necessarily mean fatal consequences. PETBOOK explains how to recognize cancer in your pet and what you can do if your beloved pet receives the diagnosis.
Recognizing the First Signs
“You can observe the lump for a while to see if it goes away. If it remains, you should go to the vet and have it aspirated,” recommends Juliane Glatz, a veterinarian at the Center for Small Animal Medicine in Neunkirchen-Seelscheid.
Because: “You can’t tell just by feeling whether something is benign or malignant,” explains Martin Kessler. He is a co-founder of the animal clinic in Hofheim, Hesse, which offers chemotherapy and radiation therapy for animals with cancer. In the worst-case scenario, however, the lump is cancer, which can spread unchecked if left untreated.
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After the Cancer Diagnosis – Surgery, Chemo, or Radiation Therapy
The good news: Nowadays, cancer in animals can often be treated successfully after a diagnosis. “There have been significant advances in treatment because we understand tumor diseases better today and can therefore treat them more effectively,” says Kessler.
However, before treatment, it must be precisely diagnosed what type of cancer it is and how far it has spread. Then an individual treatment plan is created. For some types of cancer, surgery is sufficient, sometimes combined with chemotherapy or radiation therapy.
According to Kessler, surgery costs range from about 500 to 5,000 euros, while radiation therapy costs between 2,000 and 10,000 euros. The cost of chemotherapy depends on the size of the animal, ranging from 2,000 to 5,000 euros.
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Focus After the Cancer Diagnosis – Improving Quality of Life
Chemotherapy is administered to the animal via infusion, tablets, or injection. Since animals must remain completely still during radiation, they are anesthetized for this. “Such anesthesia is the least of our problems. We’ve been doing radiation since 2001 and have never lost an animal under anesthesia,” reports Kessler from practice. But other cancer treatment methods are also possible. “It’s very individual,” says the veterinarian from Hofheim.
The therapy is generally not as burdensome for an animal as it is for a human with cancer. “The goal in veterinary medicine is different,” explains veterinarian Glatz. It’s not just about prolonging life. “We don’t want a higher cure rate at the expense of quality of life,” says Kessler.
Therefore, a significantly lower medication dose is used in cancer treatment. Any side effects should be kept as minimal as possible. Some animals have none at all. Others, however, may vomit, have diarrhea, or refuse to eat. “After a few days, the intestines regenerate, and the side effects stop,” says Juliane Glatz.
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The Risk Increases with Age
In general, the number of cancer patients among dogs and cats is rising. This is due to their increased life expectancy. The connection: The body’s repair mechanisms for genetic damage become less effective with age. “The older you get, the higher the tumor risk,” says Kessler.
In dogs, the breed also plays a role. According to the veterinarian, over 90 percent of patients with a white skin cancer of the nail bed, squamous cell carcinoma, belong to the breed of medium or giant schnauzers.
A Bernese mountain dog, on the other hand, has a 260 times higher risk of developing malignant histiocytosis than a dog of another breed. This cancer is recognizable by changes in the lungs, spleen, liver, lymph nodes, and blood. “In large dogs like Great Danes and Kangals, but also in mixed breeds, bone tumors are more common, and these are very painful,” says veterinarian Glatz.
In cats, lymphomas in the abdominal cavity are generally among the more common tumors, manifesting, for example, with vomiting and weight loss. The cat’s breed plays a minor role, as there are relatively few purebred cats. According to Martin Kessler, Siamese cats are particularly predisposed to certain types of tumors.
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How Does Neutering Affect the Cancer Diagnosis?
Pet owners can do some things to reduce their pet’s cancer risk. Similar rules apply as for cancer prevention in humans: healthy diet, sufficient exercise, and maintaining a normal weight are recommended.
Additionally, neutering reduces the risk of certain tumors, such as those in the mammary glands or testicles. “Conversely, it’s also a question of whether neutering promotes certain tumors,” Kessler points out. Recently, there have been indications that some very dangerous types of tumors occur more frequently in neutered dogs.
However, these studies come from the U.S., where many dogs are neutered in their first year of life, often even in the first six months. “Whether this applies to us in Germany, where early neutering is the absolute exception, has not yet been investigated,” says Kessler. According to the current state of science, there is no reason to forgo neutering out of fear of an increased tumor risk.
With material from dpa