We developed an easy, quick and cost-effective detection method for lymph node metastasis called the semi-dry dot-blot (SDB) method, which visualizes the presence of cancer cells with washing of sectioned lymph nodes by anti-pancytokeratin antibody, modifying dot-blot technology. We evaluated the validity and efficacy of the SDB method for the diagnosis of lymph node metastasis in a clinical setting (Trial 1). To evaluate the validity of the SDB method in clinical specimens, 180 dissected lymph nodes from 29 cases, including breast, gastric and colorectal cancer, were examined. Each lymph node was sliced at the maximum diameter and the sensitivity, specificity and accuracy of the SDB method were determined and compared with the final pathology report. Metastasis was detected in 32 lymph nodes (17.8%), and the sensitivity, specificity and accuracy of the SDB method were 100, 98.0 and 98.3%, respectively (Trial 2). To evaluate the efficacy of the SDB method in sentinel lymph node (SLN) biopsy, 174 SLNs from 100 cases of clinically node-negative breast cancer were analyzed. Each SLN was longitudinally sliced at 2-mm intervals and the sensitivity, specificity, accuracy and time required for the SDB method were determined and compared with the intraoperative pathology report. Metastasis was detected in 15 SLNs (8.6%), and the sensitivity, specificity, accuracy and mean required time of the SDB method were 93.3, 96.9, 96.6 and 43.3 min, respectively. The SDB method is a novel and reliable modality for the intraoperative diagnosis of SLN metastasis.Sentinel lymph node (SLN) biopsy is a common surgical procedure in clinically node-negative breast cancer patients. [1][2][3] An accurate assessment of metastasis of SLNs is vital for making decisions on the avoidance of unnecessary removal of axillary lymph nodes and the provision of appropriate adjuvant treatment for patients. SLN metastasis is usually detected by conventional modalities, including intraoperative hematoxylin and eosin (H&E)-based pathological examination of frozen sections, cytological observation of touch imprints or a combination of pathological and cytological examination, followed by definitive postoperative pathological examination of permanent sections.4-7 However, novel diagnostic modalities are desperately required. This is because of a heavy workload for pathology specialists in Japan and discordances between the intraoperative and postoperative pathological diagnosis of SLN metastasis, with a false-negative rate of 5-52%, [8][9][10][11][12][13][14][15] resulting in unnecessary reoperation of axillary dissection. Additionally, intraoperative touch imprint cytology (TIC) has lower sensitivity in detecting metastasis of