I don't know what causes lipomas to form but Labradors and dobermans both seem to get a lot them, based on our patients. I have an 8 year old Black Lab that started getting lumps all over it's body. Most are very close to the skin surface and feel very loose. However, some recently occurring lumps seem to be less loose. The vet took a small biopsy with a syringe about a year ago when they first started occurring and determined that it was all fat tissue.
Dogs develop fatty tumors called lipomas.
Lipomas are normally diagnosed with aspiration of the lump and this is pretty reliable. Most fatty cell tumors are not malignant but a very small percentage of them are either locally invasive or do have metastatic potential. A very small percentage. I don't know if Labradors have a particular sensitivity to these tumors but they do get a lot of them. Most dogs with these tumors will have more than one.