Fine needle aspiration (FNA) is a type of biopsy that is performed with a small (21 to 25 gauge) needle to obtain samples of tissue and fluid from solid or cystic breast lesions. It is one of the many different modalities for diagnosing breast masses outside of formal excision. Other methods include core needle biopsy (CNB) and Mammotome vacuum-assisted stereotactic biopsy. FNA and CNB can be performed with the assistance of imaging guidance (namely ultrasound) or done “free-hand” in the case of palpable breast lesions. Vacuum-assisted biopsy is performed with sonography, mammography, or MRI assistance. Controversy exists regarding which is the preferred method for diagnosing, as each has strengths and weaknesses, and their incorporation into the breast surgeon’s practice varies. FNA has many advantages and potential uses making it a popular option for the diagnosis and treatment of certain breast lesions.
The breasts of an adult female are located on the anterior portion of the chest wall and play a vital role in milk production. The breast tissue lies on the pectoralis major muscle and is supported by many ligaments that arise from either side of the sternum. Each breast consists of 20 lobes that are dispersed evenly below the nipple. Surrounding each lobe is fatty tissue that gives the breast its shape and size. Each of the lobes consists of numerous lobules which produce milk in response to prolactin and the female sex hormones. The female breast can develop cystic and solid lesions in the lobes. In general, the majority of cystic lesions are benign, and the majority of solid lesions are malignant. Breast cysts tend to develop at the terminal end of the ducts and accumulate fluid. Most breast cysts are small ranging in diameter from 5 mm to 20 mm and may fluctuate in size over the course of the menstrual cycle. A female may develop one or multiple cysts. Most of these cysts are painless, but some women may have discomfort or discover them during palpation of the breast.
Breast cysts are strongly influenced by hormones and are most common in women of childbearing age. Because of the concern of malignancy, women often seek medical attention. While a breast cyst may be palpable, sometimes it can be confused with a solid mass. Hence, one of the first approaches to management is a fine needle aspiration biopsy. Some physicians will even order an ultrasound before the FNA to determine the depth, number, and location of the cyst or cysts.
FNA is indicated for patients with a mammographic abnormality or palpable breast lesions. FNA remains controversial for the diagnosis of suspected malignant lesions due to the relatively small amount of breast tissue that is sampled and the high rate of non-diagnostic or inadequate samples. In this case, the “triple test” is performed using a combination of the physical exam, imaging studies and cytology to make this diagnosis to increase diagnostic accuracy. Though the Z0011 study is changing the treatment of axillary disease, axillary ultrasound with FNA sampling of suspicious appearing nodes is advisable.
FNA is indicated for breast cysts that are large, symptomatic, display vegetations, or imaging abnormalities.
FNA should not be done in the following situations:
The technique uses alcohol swabs, povidone-iodine solution, sterile gloves, and drapes, a 21 gauge needle with a semiopaque needle hub and a 3 ml or 5 ml syringe. A plastic bandage with soft gauze is needed to close the hole. The use of local anesthesia is not necessary unless the patient is anxious. However, if the lesion is deep and one is going to make multiple attempts, 1% lidocaine should be infiltrated in the skin area.
Fine needle aspiration can be done in a clinic or operating room. The procedure should be done in a strict sterile manner. The area of the breast should be prepped and draped in a sterile fashion. The performer should use sterile equipment including gloves.
FNA is performed percutaneously using a small needle (usually a 21 to 25 gauge). The skin is prepared with alcohol, chlorhexidine, or betadine then numbed with a local anesthetic. The mass is localized by palpation or by ultrasound guidance. The mass in question is punctured while negative pressure is created and maintained in the syringe (increasing diagnostic yield). Multiple passes of the needle are made through solid lesions. The puncture is repeated with slightly different needle trajectories to sample different territories. If the lesion is cystic, the liquid is aspirated fully. Then the samples are sent for evaluation in pathology. The area around the puncture site is check for evidence of bleeding or hematoma.
Even though FNA appears to be a simple procedure, a number of complications can occur which include the following:
So far there is no evidence to show that FNA causes seeding of breast cancer or worsens survival or prognosis. More important, FNA does not affect the number of falsely positive mammograms as long as the radiologist has prior information of where the FNA was performed.
Advantages of FNA over other Modalities
Lower diagnostic yield than core needle biopsy
Certain studies have cited the sensitivity of aspiration cytology for malignancy at 64% for one aspiration sample and 91% in patients with three samples. Specificity was 56% (inadequate or unsatisfactory cytological preparations.
If the FNA reveals a non-bloody aspirate and the cyst resolves, no more follow up is required. Some physicians do follow up with an ultrasound to ensure that the cyst has completely resolved. Re-evaluation is usually done 4 to 6 weeks later.
If the cyst persists after aspiration or contains bloody fluid, the patient should be referred to a surgeon for a formal biopsy.