This page was reviewed under our medical and editorial policy by
Henry Krebs, MD, Interventional and Diagnostic Radiologist
This page was reviewed on December 2, 2022.
Doctors use various methods to diagnose cancer and determine the best treatment. One procedure, called a biopsy, removes a sample from a suspicious mass for microscopic examination. If applicable, doctors may perform a needle biopsy, which allows access to cells inside the body without the need for surgery.
There are two types of needle biopsy: fine-needle aspiration and core biopsy. They differ by the gauge or diameter (size around) of the needle.
Fine-needle samples undergo a cytology or cytopathology examination, in which single cells or small groups of cells are studied. By comparison, core biopsies take longer to process and undergo a histology exam, which analyzes the structure of tissue and cells.
Fine-needle aspiration may be used to get samples from almost anywhere in the body. It’s often ordered to biopsy growths in the skin, thyroid or breast, and to analyze lymph nodes.
In the case of thyroid nodules, for example, a doctor typically uses ultrasound and takes two to six samples during one FNA procedure, according to the American Thyroid Association. The procedure often takes less than 30 minutes.
To access deeper areas within the body, doctors may perform a fine-needle aspiration guided by a flexible scope such as an endoscope (for the gastrointestinal tract) or bronchoscope (for the lungs).
For an FNA biopsy, local anesthesia may not be necessary, because injecting a painkiller may cause more discomfort than the needle used for aspiration. The procedure resembles getting a shot, except that instead of injecting medicine, it’s withdrawing cells and/or liquid. It may be performed in a doctor’s office.
If the target mass cannot be seen or felt easily through the skin, the doctor may rely on ultrasound or computed tomography (CT) scan imaging to precisely place the needle.
When completed as an internal procedure, FNA requires sedation and perhaps anesthesia. As part of the procedure, an intravenous (IV) line may be inserted into an arm or other location to administer drugs. The patient’s vital signs may be monitored by an electrocardiogram (EKG). After the procedure, the patient may be taken to a recovery room for observation while the sedation wears off.
If a doctor proposes a fine-needle aspiration, it’s usually to determine whether cancer is present and identify the type of cancer. If the cancer is metastatic, an FNA may check for genetic and other information indicating whether the tumor would respond to certain chemotherapies or biologic treatments. It may be a good choice for those who aren’t good candidates for more invasive biopsy methods.
Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) has greatly increased the ability to view, assess and sample masses in the gastrointestinal tract and pancreas without the need for invasive surgery. The liver, bile ducts and lymph nodes in the chest may be seen via this technique, which has improved efforts to diagnose and stage cancer.
As with any procedure penetrating the skin or organs, there’s a risk of infection, though less than from a core biopsy or surgical removal of tissue. There’s a rare risk (estimated to be less than 1 percent, according to a 2015 study) of spreading cancer cells from the target tumor back along the needle’s path (called seeding). It’s also possible for the needle to miss the tumor (causing a false negative test result), or for the needle to not gather enough cells to prove the presence of cancer.
Because a fine-needle biopsy collects small amounts of cells (and not chunks of whole tissue), it can’t answer structural questions, such as whether a breast tumor is an invasive cancer or not. Other forms of biopsy may be more appropriate in some cases.
Among the results possible from a fine-needle aspiration biopsy are:
There’s no preparation for a typical fine-needle aspiration. The procedure should go quickly, even though the doctor may take more than one sample. There’s a chance of some bleeding, bruising or swelling. Patients are typically able to get home on their own because this procedure doesn’t require sedation.
With an EUS-FNA, the patient may not be allowed to eat or drink after midnight the day before the procedure. Those who take blood-thinning medications, including aspirin, may be asked to avoid those for the week leading up to the appointment. Those who have heart or lung disease may need their doctor’s written authorization that they’re healthy enough to undergo the procedure. There’s a low risk of an EUS-FNA causing serious bleeding, infection or inflammation.