[AbiDrew85]

Two more questions:
1. If having ANY breast tissue present will make them re-grow, when someone gets a breast reduction, won't they just grow back to the size they were?

B. Why can't said breast tissue be transplanted into me to make mine grow?

It's not QUITE that simple... Mainly there's a POTENTIAL. Which further increases based on other factors...

It'd just be dead tissue transplanted into a male body with male hormones and nothing weird going on. And you'd reject it more likely than not anyways.

Usually, even when ALL known necessary factors are present, they'll never regrow fully anyways. They might not even recover anything at all for reasons not yet fully understood.

The presence of ANY cancerous cells makes it a guarantee though... But it's not a good kind of growing.