A Novel Method of Sentinel Lymph Node Mapping Using Magnetite in Patients with Thoracic Esophageal Cancer

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The sentinel lymph node (SLN) concept has been applied to breast cancer and malignant melanoma for the purpose of minimizing-invasive surgery, but its applicability to thoracic esophageal cancer is unclear. The purpose of the present study is to evaluate SLN mapping in thoracic esophageal cancer patients using a new method that employs magnetite as a tracer. Before undergoing esophagectomy, ferumoxides (superparamagnetic iron oxides) was endoscopically injected into the submucosal layer of the peritumoral region in the thoracic esophagus. Thereafter, magnetic force from harvested lymph nodes was measured ex vivo using a highly sensitive, hand-held magnetometer. SLNs were mapped in all patients using our new method. Ferumoxides particles entrapped by macrophages were identified histopathologically in the lymph nodes, confirming their migration to SLNs. The number of SLNs averaged 9.3 in thoracic esophageal cancer and SLNs was widely distributed in the cervical, paratracheal, intrathoracic and perigastric regions. Our new method employing magnetite as a tracer for mapping SLNs is applicable to thoracic esophageal cancer. However, because the SLNs are distributed widely, the SLN concept may not be the basis of less-invasive surgery in thoracic esophageal cancer.