Years ago, I lost my own personal pit bull to a fast growing brain tumor. Unfortunately, in both human and veterinary medicine, brain tumors can result for no known reason. While genetics and environment may potentially have a role, the underlying cause for brain tumors is typically unknown.
The Havanese does not have to be really light. Depending on the size of a Havanese the weight ranges from 7-22lbs. I own a very athletic agility Havanese that stands 11â³ at the withers. She weighs 18-20lbs depending on how much training she does and her muscle mass. From the AKC Standard.
A dog smaller than this, fully grown, would be considered too small and may have size related health issues. There are however, many Yorkies that are a tad larger than the 7 lbs, weighing 8 to 10 lbs. (3.62 to 4.53 kg).