The stiffness of lymph nodes containing lung carcinoma metastases: A new diagnostic parameter measured by a tactile sensor

It is believed that the stiffness or hardness of a lymph node containing a metastasis differs from that of lymph node without a metastasis because of the difference in tissue density, which is derived from the lymph node's histopathologic features. Prior to this study, however, there had been no attempts to quantify the hardness or stiffness of lymph nodes. The authors developed a new tactile sensor and system for measuring the stiffness (g/cm) of lymph nodes accurately, and they studied its utility as a tool for diagnosing lymph node metastases. Clinical specimens were obtained from 14 patients who underwent lobectomy or pneumonectomy with hilar and mediastinal lymph node dissection for nonsmall cell lung carcinoma at the University of Tokyo between January and July 1996. With the tactile sensor developed by the authors, 212 resected lymph nodes were measured for their stiffness. Among these 212 resected lymph nodes, 57 were diagnosed as containing metastases (38 from adenocarcinomas and 19 from squamous cell carcinomas). The mean stiffness of the lymph nodes that contained metastases was 3.35 +/- 1.57 g/cm, and that of lymph nodes without metastases was 1.23 +/- 0.50 g/cm (P < 0.001). Receiver operating characteristic analysis revealed that the area under the curve was 0.93, indicating excellent accuracy of the method. When the cutoff was 1.5 g/cm, the sensitivity was 91.2% and the specificity was 78.1% for detection of lymph node metastases. Measurement of the stiffness of resected lymph nodes was confirmed as an accurate approach to diagnosing lymph node metastases without knowledge of other factors, such as lymph node size or color.