Microadenoma. The MRI is very sensitive, and it can pick up tiny "lumps" in many people. The presence of a tiny adenoma does not necessarily mean there is a problem. If it is making excess hormone (eg. prolactin) then treatment directed at the hormone is important. Theoretically, "big" pituitary tumors were once small, but most micro's don't get much bigger. See your Endocrinologist.
No, but. Often no therapy required just need hormones checked and repeat mri's yearly to make sure it doesn't grow.
Yes. A microadenoma is a growth that is less than 10 mm (<1 cm). This is small and manageable. The management of this tumor depends on what it's doing (overproducing hormones or non-functioning).