癌の外科手術における磁気応用－ センチネルリンパ節マッピングと術中迅速診断－

Recently, there has been remarkable progress in the field of magnetic nanoparticles, with them now being applied in cancer surgery. During tumor surgery, lymph node dissection is required along with tumor resection. However, in cases such as breast cancer, lymph node dissection can be omitted if no metastasis is found in the sentinel lymph node (SLN; the first draining lymph node from a primary tumor), thereby reducing postoperative sequelae. The presence or absence of SN metastasis alters the surgical procedure; therefore, intraoperative SLN mapping and rapid pathological SLN diagnosis are required. The standard procedure of SLN mapping is a combination of radioisotope and dye methods, but radioisotope methods have problems associated with regulation and safety. To overcome these problems, a SLN mapping method using magnetic nanoparticles has been developed. This technique has already been clinically applied to breast cancer. In this article, a laparoscopic magnetic probe was developed to expand the SLN theory to visceral organs such as the stomach and gallbladder. A preclinical study of SLN mapping was feasible in laparoscopic minimally invasive surgery. Although resected sentinel lymph nodes can be rapidly diagnosed intraoperatively, the diagnostic accuracy of hematoxylin and eosin staining is limited. Conversely, immunohistochemistry, which gives additional information to pathologists by staining particular proteins, has not yet been used for rapid diagnostics because of the time required for staining. A new rapid immunostaining method is magnetically-promoted rapid immunofluorescence staining using functionalized fluorescent ferrite beads. The antigen-antibody reaction is accelerated by magnetic force, and antigen-antibody complexes can be directly observed with a fluorescence microscope. We have succeeded in diagnosing frozen sections within 15 min from fixation to staining. To realize minimally invasive surgery, a detailed understanding of tumor development is essential, and nanotechnology is being applied in this field to address this issue. In this paper, we introduce a SLN biopsy and rapid immunostaining method based on magnetic nanoparticle technology to further this field.