Lumps on the nect could be due to swollen lymph gland, abscessed tooth or possibly an salivary gland problem depending on where on the neck it is. Usually with a salivary gland problem you will also see excessive drooling.
Swollen lymph nodes can be due to many causes including infections, autoimmune diseases, fungal and bacterial infections and lymphoma (cancer). You can read about the lymphatic system in the dog here:
An abscessed tooth can sometimes cause lumps or swelling of the muzzle or jaw and upper neck. You will want to check your dog’s mouth and look for any broken or discolored teeth. If you find any, buffered aspirin can be given to a dog with a dosage of up to 5 mg per pound every 12 hours for pain until your dog can be seen by your Vet. Keep in mind that a dog's body does not metabolize aspirin in the same way as a human and thus should not be given more than a day or two without contacting your Vet.
Check just under your dog’s jawbone for a swelling and under your dog’s tongue for a swelling. This is where some of your dog’s salivary glands are located. If you find a swelling here, it’s possible your dog has an accumulation of fluid near the salivary gland called a sialocele which is causing your dog to salivate more. This condition does require your dog to be seen as soon as possible. You can read about it here:
A lump or growth is hard to diagnose even with an office visit, over the internet it is even harder as we can not even see the growth. A lump may indicate cancer, but many such growths are harmless. Many lumps are not painful or bothersome. It may be a fatty tissue deposit called Lipomas or a wart or a hematoma, but to be positive your vet will need to test the lump to be sure.
Any lump found on your animal should be tested to determine if it is a cancerous or benign lump. Your vet will want to perform a fine-needle aspiration or other appropriate test. It is performed quickly and allows some of the cells of the lump to be evaluated by the veterinary pathologist. This test will allow the vet to determine the nature of the lump and take the necessary steps to remove it. Some vets will leave it alone if it is not serious. If it is an abscess, he may just drain it and prescribe antibiotics. Lumps that are solid feeling, feel attached and fast growing should be checked as soon as possible as these are the ones that are more likely to be serious.
Here are a few sites for additional information and pictures to allow you to get an idea based on the physical characteristics..
Picture of Lipoma
Picture of Hemangiosarcoma
Picture of a mast cell tumor
(mast tumor site)
Information on Canine Oral Papilloma virus
I hope you find this information helpful.