Hello, thanks for your question today! I am Dr. Drew, and I am a licensed veterinarian. I'll be happy to help you in any way I can.
While many lumps and bumps are just benign cysts or other harmless growths,
some can be malignant (cancerous), and therefore it is wise to have some simple testing done by your veterinarian.
The usual test is a Fine-Needle Aspirate, which does not require anesthesia or sedation in most cases,
and can yield results within a few minutes, or a few days if it must be sent off to a laboratory for interpretation.
Now, the presence of clear fluid would tend to point to a benign cyst,
but I'd still rather play it safe and have an aspirate performed on it.
Especially in an elderly dog like Sam, the likelihood of it being cancer, would be increased.