My Guinea Pig Has A Large Lump, What Could It Be?

From your description in the question it sounds like there is a possibility that your guinea pig may be pregnant. Although pregnancy is hard to detect in guinea pigs at first, there are some signs that you could watch out for.
During the first week of pregnancy there will be no signs or symptoms. The only indication in the second week may be that the sow may start to drink more water. Week three will mean that the sow will start to gain more weight which means that the abdomen muscles will tighten. In week four, an experienced guinea pig breeder will be able to feel fetuses. Week five will mean that the sow will be beginning to look pregnant as her belly will start to become more rounded. You will almost definitely be able to feel the fetus' outlines. During week seven you may be able to feel the babies kicking. Week eight may mean that sow will find it difficult to move around, although she will be able to feed and drink as normal. Week ten is when the babies will be born.
However, there is also the chance that this could be a tumor developing in your guinea pig. There are several signs that you can look out for to give you more of an idea. First of all, is the lump rapidly growing bigger? Is it bleeding or leaking liquid? Is the lump an extension of the skin or does it feel like it is separate? Does it feel warm? Does it appear to cause your pet any pain? Does the lump feel like it is attached to the skin? Although all of these may point towards the diagnosis of a tumor, it is best to take your pet to a vet as soon as possible as they will be able to diagnose best.

My guinea pig has a lump the size of a golf ball on its side, it doesn't move under the skin. My guinea pig is still eating and playing with friends he doesn't seem ill with it. What shell I do?

You can determine to some extend if it is tumor or not by watching few things carefully. Look for its shape, is it irregular. Is the lump growing rapidly? Is the lump bleeding or some liquid coming out of it? If the lump seems to be skin's extension or it seems to be a bud just attached with the skin. Is it warm and causing pain? If it is under the skin, is it well attached with skin tissues? Are all these things somehow point towards tumor? But still for confirmation you should take your pet to vet soon and get its biopsy test immediately.

Its common for Guinea pigs to get lumps as they get older. If you can move the lump around under the skin then I wouldnt worry about it if I were you however if you can't move it about if I were you id take the guinea pig to the vets and get it checked out because the vets might think its best to get it removed, I can't make any definite decisions on what would be best to do without seeing the guinea pig

My pig is coming up to eight years old, I don't know how the poor thing was able to last that long. Unfortunately now, he has what appears to be a large tumor under his neck, to the left side. He looks like he is in pain, and there hasn't been feces in his cage for a week. I don't think it's worth taking him to the doctor, he had a very long life for a little piggy.

She might be pregnant hold on to her stomach for a while and see it you feel any moving if so those are her babys

I have a question as well, My guinea pig Electra is sweet but doesn't want me to hold her, her sides are hard, I feel little lumps on her sides and the lady in the pet shop told me she might be pregnant, but Ive had her since December 19, 2010 to today about 56 days so far and the lumps aren't very big, so what could it mean, I really want some babies, But I'm not sure PLEASE HELP A-S-A-P!!!!! :'(

You should look at the tumor. Try and brush the pig's hair back, and see if you can see the tumor. If it looks kind of like a 'white-head zit' you should see the vet. And if it's tumor it developing quickly or oozing out liquids, you should make a doctor's appointment for your Piggy.

Mine has a massive lump under its belly but my mam says that we should not take it to the vets because its very old now its 4 years old but I don't want it to have a painful death if it dose die I'm going to cry . :(:(:(:(:0

Its common for guinea pigs to get lumps as they get older if the lump can be moved under the skin I wouldnt worry about it if I were you however if it can't be moved about under the skin then I would take it to the vets to be checked out or removed however if your guniea pig is quite old I wouldnt recomend getting it removed

He has two lumps but only one is large. One on his stomach and one on his shoulder. The one on his stomach bleeds and the one on his shoulder is the size of a tennis ball. He acts normal sometimes but somethings he won't come out of his little house. He gets feed every day and always has clean water.
What could these be?