Home » Pet Health » Cancer 101 » Signs and Symptoms to Watch For in Dogs


Early detection of cancer in dogs is important when it comes to treatment. By regularly monitoring your dog’s habits and behaviors, you may be able to detect early signs of illness, including cancer. If your dog shows any of the following, do not hesitate to consult your vet:

    1. Loss of appetite: Dogs love to eat. If your dog starts ignoring food, this may be a sign that something is wrong. It is possible that your dog is suffering from nausea, which can be associated with many things, including different types of gastrointestinal cancers. This kind of loss in appetite usually leads to weight loss, which is another sign that something may be wrong.
    1. Difficulty eating or swallowing: In addition to nausea, sometimes abnormal growths can make it difficult for your dog to eat. A lump in the mouth makes it difficult to chew, while an unusual swelling in the neck can put pressure on the esophagus (the tube between the mouth and the stomach), leading to difficulty in swallowing. When checking your dog, look for signs of new bumps and lumps and have your vet check them out.
    1. Abnormal weight loss: A loss of weight that is not due to diet changes or exercise can indicate illness in your dog. If it is cancer, such as lymphoma, lymphosarcoma, or a growth in the intestines, it may be impacting your dog’s ability to eat. To find out what is causing your dog’s weight loss, consider visiting your vet as soon as you notice the changes.
    1. Bleeding or discharge: Unusual discharge from the nose, mouth, eyes, ears, vulva, vagina, or anus may be concerning. Discharge, including bleeding, isn’t always a sign of cancer, but it is worth checking. For example, bleeding from the mouth or anus could result from cancer in the gastrointestinal tract. Therefore, it helps to have your vet check things out.
    1. Presence of an unpleasant odor: Most dogs naturally have odorous breath and skin. If you notice an unusually unpleasant smell emanating from your dog (even with regular grooming), this could be a sign of illness. Sores, lumps, strange odors, bleeding gums, or change in gum coloration are signs of oral cancer. If you notice a growth in your dog’s mouth (or on its skin), it may contain bacteria that cause the unpleasant odor. Because most pet owners do not examine their pet’s mouth, oral cancer can often go unnoticed
    1. Non-healing sores: These are skin wounds that do not seem to heal despite oral antibiotics or topical ointments. Your dog can also get sores near a nail that do not heal. Often, pet owners attribute non-healing wounds to obsessive licking behavior, but it might be more than that. Keep an eye on wounds and sores that do not heal.
    1. Reluctance to exercise: If your happy, active dog is suddenly not interested in playing or going out for a walk, it may be typical behavior if your dog is old or finds it too warm. However, sluggishness might mean that your dog is not well and needs medical attention. A loss of stamina can be due to illnesses like a tumor on the heart or lung that cause difficulty breathing. In addition, adrenal gland tumors may result in tiredness or lack of interest in exercise.
    1. Persistent lameness or stiffness: Although your dog will likely experience stiffness or limping at some point in its life, if it persists, it may be a sign of something that needs your vet’s attention. Some cancers, like those in the nerves, muscles, or bone, can result in consistent limping, lameness, or stiffness, thus affecting your dog’s movement. You might also notice an abnormal growth or swelling along the legs that causes concern.
    1. Evidence of pain: General pain or discomfort is a sign that something might be wrong with your dog. If your dog whines or cries at your touch and there is no apparent injury, consult your vet to determine what’s causing the pain.
    1. Abdominal swelling: A swollen belly might indicate an accumulation of fluids, sometimes caused by a tumor in the abdominal area.
    1. Difficulty passing stool: Changes in the water intake or the frequency of urination can indicate a problem, like cancer of the kidneys or bladder. In addition, cancer in the gastrointestinal tract or gut (particularly in the rectal area) can make it difficult for your dog to pass stool. If you notice these symptoms in your dog, consult your vet.
    1. Persistent coughing: This is not a symptom that automatically signifies cancer. Smaller dogs tend to develop coughs because of shorter windpipes. Occasional coughing is not an issue, but if it persists, your dog may have cancer of the lung or windpipe (often caused by second-hand smoking).
    1. Abnormal swellings or lumps that increase in size: Make it part of your weekly routine to check for lumps, bumps, or skin changes. If something feels strange to you, make an appointment to get your dog checked out by your vet.
    1. Collapsing: If your dog collapses unexpectedly, contact your vet. Even if the dog feels better the next day, have them checked out, as this could signal something abnormal. For example, a tumor in the spleen might lead to your dog collapsing.
    1. Seizures: Seizures in pets can be scary, but they can mean different things. Watch for uncontrolled bursts of movement such as jerking legs or foaming at the mouth (like an epileptic seizure). Seizures are more likely if you have an older dog. If your dog has a seizure, have your vet examine them as soon as possible, as seizures can sometimes result from a sign of a brain tumor.

All these symptoms can be alarming when you notice them, but do not hesitate to consult your vet. They can help you understand what’s going on with your dog and provide you with the necessary care options.

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Last Updated: May 10, 2022

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