A doctor performs a thyroid biopsy, according to WebMD. There are three types of biopsies, including fine-needle, open and core needle biopsies. The purpose of the biopsy is to determine if cancer is present in the thyroid.
During a fine needle biopsy, the doctor puts a thin needle into the thyroid gland from the skin, notes WebMD. Open biopsies involve cutting into the skin to observe the thyroid gland. A core needle biopsy uses a needle equipped with a special tip that removes a rice-grain-sized piece of tissue for testing. Physicians generally order thyroid biopsies to investigate the cause of a thyroid nodule or goiter.