How is EUS FNA performed?
- EUS is performed with a linear array scope, which provides an image along the long axis of the scope. This allows the endoscopist to visualize the exact position and action of the needle in sonographic real time.
- The flow and Doppler capability of this instrument allow for visualization of vascular structures that need to be avoided to perform a safe tissue sampling.
- The 19- to 24-gauge aspiration needle, with a stylet, is introduced through the scope channel and under direct ultrasound visualization is advanced into the area to be sampled.
- Once the lesion has been entered, the stylet is advanced to the original position to clear any nonlesional tissue possibly adherent from the passage of the needle through the GI tract.
- Suction is then applied with a syringe to the proximal end of the needle. Sometimes several passes are performed to ensure that enough material is obtained.
What are the advantages of EUS-FNA over other sampling modalities?
- EUS-FNA allows definitive cytologic diagnosis of both primary and metastatic lesions and thus permits staging of the primary tumor, regional lymph nodes, and metastatic lesions (the TNM system).
- Patients undergoing evaluation of a suspected GI wall malignancy often require an EUS examination to obtain tumor staging information (depth of penetration of lesion through the GI wall) of the lesion.
- Nodal (N) staging with tissue acquisition can be performed in the same setting. EUS-FNA can also be useful in determining the presence of distal metastasis (M) such as to the liver.
- In addition, EUS-FNA allows the sampling of extremely small lesions, including pleural and ascitic fluid collections that cannot be obtained by other means (such as computed tomography [CT]–guided biopsy).
- In general, EUS staging accuracy appears to be better than all modalities except surgical exploration.
What is the sensitivity and specificity of EUS-FNA for the diagnosis of malignancy?
- The sensitivity and specificity of EUS-FNA for diagnosis of malignancy depends on the type of tissue being sampled
Sensitivity and Specificity of EUS-FNA
| Tissue | Sensitivity | Specificity |
|---|---|---|
| Pancreatic cancer | 90%-95% | 90%-100% |
| Mediastinal lymphadenopathy | 88% | 90%-100% |
| Periintestinal lymphadenopathy | 70%-90% | 93%-100% |
| Mucosal and submucosal lesions | 50%-90% | 80%-100% |
EUS, Endoscopic ultrasound; FNA, fine-needle aspiration.
What is the role of EUS-FNA in the evaluation of mediastinal lymphadenopathy?
- EUS with FNA is the diagnostic test of choice for evaluating mediastinal lymphadenopathy.
- It has been found to be particularly useful in patients who have non–small cell lung cancer (NSCLC).
- In patients with NSCLC, the most significant predictor of long-term survival is the presence of metastasis within regional bronchopulmonary or mediastinal lymph nodes.
- In a large metaanalysis, EUS-FNA sensitivity in mediastinal nodes was 88% (95% CI: 85.8%-90%), and specificity was 96.4% (95% CI: 95.3%-97.4%).
- EUS-FNA is safer and more cost-effective than other more invasive methods of sampling, such as mediastinoscopy or thoracotomy.
What are the risks of EUS-FNA?
- The risks of EUS-FNA are thought to be extremely low, given the small diameter of the aspiration needle.
- In addition to the usual risks of any endoscopic procedure (bleeding, perforation, sedation risk) a 0.5% overall complication rate was reported in a multicenter trial predominantly from infectious or hemorrhagic events. EUS-FNA of the pancreas has a very small risk of acute pancreatitis, probably less than 1%.
Is there a risk of biopsy tract seeding when EUS-FNA of a suspected malignancy is sampled?
- Yes, although the amount of risk has been found to be very low.
- Comparative studies have found that there is less risk of seeding with EUS-FNA when compared with percutaneous CT-guided FNA biopsy.
