Symptoms of cancer in pets, such as weight loss, difficulty breathing, and lumps, are not unique to cancer and can indicate other diseases as well. For instance, weight loss could be caused by diabetes, thyroid issues, or gastrointestinal disorders. Difficulty breathing might result from respiratory infections or heart disease, while lumps could be benign tumors or cysts. These symptoms are general indicators of illness and warrant veterinary evaluation. Accurate diagnosis requires comprehensive examination and tests, as only a veterinarian can determine if cancer or another disease is present.