Predicting Malignancy Using Endoluminal Ultrasound Characteristics in Mediastinal Lymph Nodes

Lung cancer is the leading cause of cancer-related death in the United States with a 5-year survival rate of 15,7%.1 In lung cancer and other malignancies, such as esophageal cancer, accurate staging is essential to establish prognosis and for patient management. Staging will help determine if surgery, chemotherapy, radiation therapy, a combination of these, or a palliative approach is the most adequate.2,3

Assessment of lymph nodes (LNs) for invasion by metastasis is undertaken if patient management is influenced by a positive or negative result. In non-small cell lung cancer (NSCLC), mediastinal LN invasion by malignant cells is a critical factor to determine if a patient is considered as a surgical candidate or not.2 In esophageal cancer, LN metastasis may be found in the mediastinum, the neck and the abdomen.4 Invasion of these LNs must be considered in the selection of treatment of esophageal cancer.3,4

There is no single method to investigate mediastinal LN invasion. Hence, a patient may have to undergo several tests and procedures. Noninvasive and invasive approaches are employed. Within the invasive techniques, endoscopic ultrasonography with needle aspiration (EUS-FNA) and endobronchial ultrasonography with transbronchial needle aspiration (EBUS-TBNA) are gaining importance in mediastinal staging.5 They provide ultrasonographic images and permit needle aspiration under direct vision for cytology specimen analysis. As more evidence is being accumulated on these staging approaches, the number of cervical mediastinoscopies, considered as the gold-standard for mediastinal staging, is diminishing.6

Characteristics of benign and malignant LNs using ultrasonography have been described in various contexts. Cervical and axillary LNs provided accurate characteristics (eg. shape, short- to long-axis ratio, number of blood vessels in LN, vascularization pattern, etc.) in predicting malignancy with linear superficial transducers.7-11 LN characteristics using EUS or EBUS also have established criteria predicting mediastinal LN malignancy (eg. size, shape, borders and echogenicity).12 Depending on the studies, it has been suggested to obtain specimens of all accessible LNs without considering their characteristics. It has also been suggested to proceed to a selective LN aspiration based on LN characteristics, with the advantage of cost reduction (fewer needles used, less time to carry out procedure, and specimens needed to be analysed).6

Color Doppler LN characteristics with endoluminal ultrasound (US) is only mentioned in a small number of studies and needs to be further investigated.13,14 With the good results obtained with superficial US, it seems reasonable to believe that color Doppler characteristics would increase accuracy in detecting malignancy of mediastinal LNs with endoluminal US.