A lump next to guinea pigs nipple

Question
while cleaning my pet i noticed a small white mark next to his nipple. I admit being a curious person i put on rubber gloves and had a bit of a feel around and found a lump which moves. I gave it a squeeze and clear liquid came out, during this process he did not fight or resist what i was doing so i assumed it did not hurt. Im now worried that he's ill as i googled nipple leakage and every website said leaking non-females is not good. Could it be cancer? I dont know how id tell my 5yr old daughter if he was seriously ill. Please help!

Answer
A typical malignant tumor or lump does not drain any liquid. Also, malignant lumps are characteristically adhered to tissue, making it difficult if not impossible to move it around. When a doctor does an exam on any questionable lump that's the first thing they check: can it move freely. If you can lift it and move it easily, chances are it's nothing serious.

I truthfully doubt this is a cancer. But the best thing to do is just watch it and see if it grows. Cancerous tumors grow, they don't just stand still. This may be just a small cyst of some kind.  Personally I would be comfortable just keeping an eye on it and watching its size. If it's getting bigger, then a trip to the vet is in order to perhaps discuss a biopsy.

An easy way to watch the growth or change in a lump is to take a black pen and make a circle around the spot. That way you will be able to see if it begins to extend beyond that border. This is one of the methods we use in the clinical setting to evaluate swelling or redness on human patients. It's actually the most effective way. It eliminates the guessing.

With all cavies the number one symptom of how they feel is their appetite. When they don't feel good they quit eating. So if he's still active and eating well it's very likely nothing to be worried about.

I'd give it at least a week and see if there are any changes. Then you can make a decision as to whether you think a vet is indicated. In the meantime I would certainly not tell your daughter   there's anything wrong. Don't upset or worry her unless you know for sure there's something to worry about.