These are basically fat lumps. Sure, okay they're “tumors” but the
cell type is just fat. So while they are 'neoplastic' the cells involved
aren't rogue. They don't recruit and the don't go elsewhere in the
body. The liabilities come from letting them grow huge. Then they have
WEIGHT and pull and stretch on stuff. If they stay small in benign areas
like the sides, belly and back – we can leave 'em alone.
How do they happen?
The dog has a layer of fat cell. Then one day they get to an age where
Lipomas can “happen” and some fat gets a little knock. Some lipoma (fat)
cells get 'loose' from the regular fat and are isolated.
“No Man is An Island” so they say. But lipoma cells are.
These errant fat cells just decide to grow and divide and make their own
private lipid / lipoma / fat “island” and that's a lipoma. This is why
they happen in areas that get knocked bumped slept on all the time. The
breastbone is the most common area.
ALSO there's a genetic “thing” at work: Labradors and other Rettrievers
get Lipomas more than other dogs. So it's more than just
fat-tissue-trauma => There's a hereditary piece too.
“If it grows it goes” because if they get heavy, or they get big near an
eye, groin, lower leg or foot, they can be quite disruptive. Otherwise
we leave 'em alone.
It is important to confirm if you are not entirely sure they're liomas.
The veterinarian should endeavor to be “pretty sure” or completely sure
before brushing them off.