In my first litter of this breed one of the puppies developed a small, pea-sized lump on his abdomen which disappeared after a day or 2 so I never thought anything of it. This was a litter born late May 2011. Esme had another litter early last year and none of those pups were affected.

Mo (who was from the 2011 litter) has just had her 1st litter, and a number of the pups are developing the lumps, which again disappear quickly. They are always on the abdomen,  nowhere else.

Does anyone have any idea what they may be? They don't seem red, hot or itchy and don't come up in a head as a spot would.

puppy pyoderma?? 
http://www.bing.com/search?q=puppy+pyoderma&form=IE10TR&src=IE10TR&pc=MASBJS

I've had that in a puppy as well; a single small hard lump under the skin that disappeared after a few days. We never did find out what it was, and the pup's perfectly healthy.

Don't think it's puppy pyoderma, those photo's look quite angry, and they aren't worried by them at all. Very odd, just wondered how common it was...

I would be very interested to know what these lumps are as well. In a litter I had I would describe them as being fairly solid and slightly movable under the skin. Just like Pedlee's litter they were only on the abdomen and formed quickly and then disappeared in two or three days. I have only seen them in one litter but the dam and puppies were very stressed before birth due to it being a massive sized litter for the bitch to carry. My guess is the lumps are linked to lowered innate immunity and in my litter they appeared at about seven weeks old. One puppy had three or four lumps and several others only the odd lump. I showed the worst affected puppy to an experienced Vet but he had never seen it before and had no idea.

Could it be what's called a 'floating rib'? It sounds similar to what one of my pups had years ago and I'd pointed it out to the vet.

My pup's lump was down in her groin; it was between the skin and the intact muscle wall.

I've no idea if this will work but here is a photo (http://s24.photobucket.com/user/pedlee/media/lumps_zps6c5e66ec.jpg.html). These lumps came up on Sunday, which is when the photo was taken, and by yesterday they had completely gone. Most pups have had a single lump, this chap had 3.

They're larger than the lump my girl had - hers wasn't visible, it could only be felt.

Exactly the same type of lump as on my puppies Pedlee. On my puppy who had several they were more widely spread out and a little smaller. The same bitch who gave birth to the affected puppies has had another litter recently and I will be checking them as they grow to see if it happens again.

Somebody else has said that she was told it's from them laying in the damp. How true that is I've no idea, but my pups are outside 90% of the time at the moment and prefer to lay on the grass (what's left of it) or paving slabs. Both my affected litters have been May/June time, the unaffected was a Winter litter, so I don't know if that has any baring on it.

I don't think laying in the damp could have anything to do with it. My affected litter was born at the time of year when it was too cold and windy to be outside. As I said before I would take a guess it's something to do with the puppy's immune system and as it affects several in a litter it could be linked to the dam's status. Probably quite simple to explain if we could find the right Vet to answer the question.