Here is another follicular neoplasm (a follicular adenoma histologically) that is surrounded by a thin white capsule. It is sometimes difficult to tell a well-differentiated follicular carcinoma from a follicular adenoma. Thus, patients with follicular neoplasms are often treated with subtotal thyroidectomy just to be on the safe side.

Fine needle aspiration (FNA) cytology can be utilized to obtain cells from a thyroid lesion for diagnosis.