Thyroid adenomas tend to be solitary nodules confined to one lobe of the gland, whereas nodular goiters tend to be generally enlarged, and multiple nodular changes in the thyroid gland are often seen bilaterally.
On gross pathology, thyroid adenomas are single nodules, often with an intact envelope and clearly defined by the surrounding tissue. Nodular goiters, on the other hand, tend to have no intact envelope and the surrounding thyroid tissue is abnormal and poorly defined.