Whats the treatment for follicular adenoma thyroid nodules?

None (in theory): If everyone is certain that the nodule is a benign tumor, or adenoma, no treatment is necessary. The problem is that cells from follicular adenomas & follicular cancers can look identical. However, somewhere in the cancer, cells are growing through the capsule or into blood vessels or lymph vessels. So most follicular adenomas are removed to make sure a follicular cancer is not missed.

Observe or surgery: It depends how the diagnosis was reached. If this was through a needle biopsy, you may have to remove. If this is the final diagnosis then you are done. To rule out thyroid cancer they usually need to see the capsule.

Watch them: Unless they are large, the treatment for adenomas of the thyroid is observation. They are removed when they are bug enough to cause symptoms.