Mass in neck

Question
My female boxer is approximately not yet two years old. She has had no health problems to date. The last 24 hours she has been very lethargic. She is eating normally, if not more; she is very thirsty; she appears to have fever. I discovered a very large mass on her neck. It is soft and does not appear to be painful to the touch and is located in the middle of the neck. It is approximately five inches in length and three inches in width. It is subcutaneous and can be seen without stretching of the skin. We are very worried as the research I've done suggests that thyroid cancer is prevalent in boxers. Thank you very much for your time.

Answer
Masses of this size or any mass should always be evaluated by a veterinarian. Lethargy, etc leads me to think that this may be an abscess or some sort of infection. If she is off her food tomorrow you should call the vet. If not, call on Monday and get her in.