Endoscopic ultrasound-guided fine-needle aspiration biopsy. An endoscope that has an ultrasound probe and a biopsy needle is inserted through the mouth and into the esophagus. The probe bounces sound waves off body tissues to make echoes that form a sonogram (computer picture) of the lymph nodes near the esophagus. The sonogram helps the doctor see where to place the biopsy needle to remove tissue from the lymph nodes. This tissue is checked under a microscope for signs of cancer.