to the best of my knowledge...a tender gland indicates a fast moving infection...imagine a shooting star...bright, then burns out in a flash like a cold making you ill for a few days then going again.
with a cold/flu glands fill up with liquid quite fast, causing them to be tender
with lymphoma and other serious causes, the glands gradually notice the underlying impurities in your body, so the grow more gradually, likely to be less tender.
Ask a Dr on the physics of glands.