A solid benign thyroid nodule that is not a goiter and normal tsh levels. what is it?

Adenoma: If there is a solitary thyroid gland nodule, that has been removed and examined under a microscrope using sections taken from the tumor, is called an adenoma. If there is invasion, then it is a carcinoma. There are some rare benign tumors (teratoma, solitary fibrous tumor, trabecular hyalinizing tumor) that could be a benign thyroid tumor.

A growth: If it's indeed "benign" (by biopsy) and the TSH is "normal", then this is just a growth on your thyroid (just like a growth anywhere else). The problem with biopsy is not all the nodule is cancerous, that is, there could be a little fleck of cancer within the nodule that can be missed during the biopsy process. That's why we recommend serial followup and not just stop after a benign biopsy.

Nodule: I presume its been biopsied. If its benign it likely represents inflammation from autoimmune thyroid disease. Continue to monitor it carefully - if it is single and getting larger it may require a second biopsy or removal.