Endoscopic ultrasound making resonance in cancer research

Endoscopic ultrasound (EUS) is a novel technology that is being increasingly used for the diagnosis and management of cancers involving various organ systems. The technology was introduced three decades ago and its use has expanded exponentially in the past two decades. EUS-guided fine needle aspiration (FNA) is the best modality for tumor detection and tissue diagnosis even if the mass is weakly identified by other imaging modalities (1). EUS-FNA is capable of taking samples from masses that are not imaged by computed tomography or magnetic resonance imaging and lesions too deeply encased by adjacent vascular structures to allow percutaneous biopsy (2). EUS-guided FNA as well as EUS guided Trucut biopsy (TCB) has proven to be beneficial for benign and malignant diseases as well as staging of malignant tumors of the GI tract and adjacent structures (3). The application of EUS-guided therapy is especially appealing for malignancies because it provides accurate and effective palliative treatment. This is possible primarily due to two EUS characteristics: (I) its ability to deliver direct treatment to lesions unreachable by other means; and (II) the minimal invasiveness of EUS, which provides superior results with a low complication rate (4). EUS is being used to locally stage esophageal tumors (T staging), and it can be used for the assessment of esophageal submucosal tumors as well. Based on the EUS characteristics, we can positively identify the lesions that arise from exterior layers. This approach is particularly useful for evaluating invasion of local disease (especially esophageal cancer), tumor depth, nodal involvement, and detection of distant metastases (5). CT and magnetic resonance imaging lack the ability to differentiate the layers of the esophageal mucosa. Thus, these modalities cannot accurately discern the T stage of esophageal cancer (6). Therefore, EUS is a prerequisite before performing esophageal endoscopic mucosal resection (EMR) or endoscopic submucosal dissection (ESD). Esophageal leiomyomas, esophageal cancers, cystic lesions, lipomas, vascular lesions, and esophageal extraluminal compressions are some of the lesions that are commonly identified using EUS. EUS can be used to obtain cytology specimens from mediastinal nodal enlargement for the diagnosis and staging of bronchogenic carcinoma (7). EUS has a definitive role for evaluation of early gastric cancers and gastric submucosal lesions. Early gastric cancers can be staged using EUS and the feasibility of EMR or ESD can be determined. Gastrointestinal stromal tumors (GISTs) and other submucosal lesions can be diagnosed as well using EUS and their potential for ESD can be determined using EUS.