The thyroid--a butterfly-shaped gland located beneath the voice box--regulates the body's energy level. The thyroid can become enlarged for many possible reasons, the Mayo Clinic explains. A biopsy, removal of cells from the thyroid for examination under a microscope, is the most accurate way to determine if a growth in the thyroid is benign or cancerous.
Fine-needle Aspiration Biopsy
Most patients undergo a fine-needle aspiration biopsy, FNA biopsy. In this type of biopsy, a tiny thin needle is inserted into the thyroid lump to draw out cells and fluid, the American Cancer Society explains. Doctors, who perform this procedure in their office or clinic, draw samples from different parts of the growth. Often, an ultrasound machine is used during the procedure to guide placement of the needle, the Mayo Clinic reports.
Surgical Biopsy
Surgical biopsy, removal of the entire lump, is performed if results from the needle biopsy are inconclusive, the American Cancer Society reports. This can occur if the sample drawn with the needle biopsy lacks sufficient cells or if the cells are atypical. Patients receiving surgical biopsies are given anesthesia to put them to sleep and the procedure is performed in an operating room.
Preparation for Biopsy
Prior to a fine-needle aspiration biopsy, a doctor may inject a numbing medicine into skin over the thyroid lump, which is called a local anesthetic, the American Cancer Society explains. In some cases, however, anesthetic is not needed.
Patients should tell their doctor before the procedure if they have a possible bleeding problem, such as that caused by taking an anticoagulant.
Diagnosis
A pathologist examines the thyroid cells under a microscope. The characteristics of individual cells and patterns in cell groups that look different from normal cells form the basis for diagnosis, according to the Mayo Clinic. Sometimes the pathologist can even tell what type of cancer is present. One clue is whether the cells are differentiated, meaning they look like other thyroid cells, or undifferentiated, an immature cell that grows rapidly.
Outcome
The majority of thyroid lumps, about seven out of 10, turn out to be benign, the American Cancer Society reports. These lumps may get bigger, but they wont grow beyond the thyroid gland itself. Thyroid cancer is found in only one out of 20 fine-needle biopsies.
About two out of 10 biopsies need to be done again because not enough cells were obtained to determine the cause for the growth.
