Electrical impedance scanning: a new technique in the diagnosis of lymph nodes in which malignancy is suspected on ultrasound

Differentiation between inflammatory and malignant lymph nodes by ultrasoun d is difficult. Electrical impedance scanning (EIS) is a new diagnostic too l, so far used primarily for the identification of malignant breast lesions . Cancer cells have altered dielectric properties compared with normal cell s, thereby distorting the local electrical field. The induced changes in ca pacitance and conductivity are measurable using EIS. We evaluated EIS in de monstrating the cause of lymph node enlargement. 51 lymph nodes that were s uspicious for malignancy on ultrasound (32 patients, mean age 32 years), wi th a mean size of 18 mm x 12 mm x 10 mm, were examined. The following lymph node locations were included in the study: cervical, inframandibular, axil lary, paraaortic and inguinal. EIS results were compared with histopatholog ical and follow-up findings. 30/34 malignant lymph nodes were correctly det ected using EIS, while 14/17 inflammatory or benign lymph nodes were correc tly identified as benign by EIS; thus, there were 4/51 false negative and 3 /51 false positive cases. The sensitivity was 88.2% and the specificity was 82.4%. Corresponding negative and positive predictive Values were 77.8% an d 90.9%, respectively. Results from this initial study suggest the potentia l usefulness of EIS as an adjunctive imaging modality in the differentiatio n of lymphadenopathy that is equivocal on ultrasound. The best accuracy was obtained in the cervical, axillary and inguinal regions. Owing to technica l restrictions of the present system, examination of inframandibular and pa raaortic lymph nodes should be limited to special cases.