It's fat!
My doctor is an expert in exotic animals, like Basenjis, and explained to me what these lumps are because my boy, "Cauy," had some. She said they were palanomas and they're common with the breed. They're not threatening and in fact are simply lumps of fat that are loose and unconnected but are right under the skin. However, there are many kinds of lumps a Beaseni can attain, both good and bad. My doctor knew how to determine the difference. Therefore, I highly recomend you see a vet to make sure, and one that specializes in Basenis.