Can elastography replace fine needle aspiration?

Abstract

Endoscopic ultrasound (EUS) is one of the best diagnostic methods for diseases of the digestive tract and surrounding organs. Whereas EUS-guided fine needle aspiration (FNA) has been very useful for providing histological confirmation for previously hard to reach lesions, elastography is aiming to obtain a "virtual biopsy" by assessing differences in elasticity between the normal and pathological - usually malignant - tissue. A question that arises is whether EUS-elastography has reached a stage where it might successfully supplant the use of EUS-FNA in some of its clinical indications. The main indications of EUS-guided FNA are listed in this article and published data on the usage of elastography in these settings is reviewed for each one. In some of the indications, a plethora of studies have been published, notably for the evaluation of solid pancreatic masses and lymph nodes, while in others there is little relevant data (submucosal masses, left liver lesions, left adrenal masses), or elastography simply is not suitable as a diagnostic means (cystic lesions). Our conclusion is that elastography is not yet ready to replace EUS-FNA in its indications, but should complement it in various settings, especially for the assessment of lymph nodes. It can only be considered an alternative on a case-by-case basis, in situations where FNA is regarded as a contraindication. Furthermore, it could be used in conjunction with other imaging techniques, such as contrast-enhanced EUS, in order to further improve the accuracy of non-invasive EUS assessment, possibly making the case for a more limited or targeted use of EUS-FNA in selected cases.

Keywords: Elastography; endoscopic ultrasound; fine needle aspiration.

Figure 1

A patient with chronic pancreatitis. The elastography image in the left panel shows a heterogeneous green pancreatic mass (red circle). B-mode reference image is shown in the right panel

Figure 2

A patient with a malignant pancreatic tumor. The elastography image in the left panel shows a homogeneous blue pancreatic mass (red circle). The mean value of the strain histogram is also shown near the bottom of the image (red rectangle). B-mode reference image is shown in the right panel

Figure 3

A patient with a benign lymph node. The elastography image in the left panel shows a mostly green mass (red circle). B-mode reference image is shown in the right panel

Figure 4

A patient with a malignant lymph node next to a primary tumor. The elastography image in the left panel shows the blue primary tumor partially encompassed in the regions of interest (pink outline) and the probably malignant satellite lymph node behind it (red outline). The node cannot be punctured without passing with the fine needle aspiration needle through the tumor. B-mode reference image is shown in the right panel