A. You are correct in stating that lipomas are very common in retrievers. Your concern about goldens and cancer is also well founded.
Lipomas are typically very easy for an experienced veterinarian to differentiate from most other tumor types by using simple palpation. If there’s any doubt, it is not overly involved or painful/stressful for a veterinarian to aspirate a questionable mass. Aspiration material from lipomas, when spread across a glass slide, will reveal obvious fat, and sending it to a laboratory is in most cases unnecessary.
To aid in lipoma control, I’ve had success using Mega Lipotropic by Best For Your Pet, Lipocomplex by Progressive Labs, and the herbal formulation Chih ku & Curcuma by Seven Forests.