Described is a novel real-time multiplex reverse transcription-polymerase chain reaction (RT-PCR) assay suitable for intraoperative detection of micrometastasis (MM) in sentinel nodes (SNs) dissected from patients with clinical N0 (cN0) gastric carcinoma.

One hundred three patients with gastric cancer, who were preoperatively diagnosed with cN0 and clinical T1 or T2, were enrolled. The patients underwent SN mapping followed by standard radical gastrectomy with lymph node dissection. In addition to all SNs, non-SNs (NSNs) within the SN lymphatic basin and NSN from a different lymphatic basin were randomly sampled. All SNs and NSNs were examined by routine histologic diagnosis and RT-PCR for the expression of cytokeratin (CK) 19, CK20, and carcinoembryonic antigen (CEA).

The RT-PCR assay and histologic examination were performed in 512 SNs and 299 NSNs from 103 patients. Pathologic l lymph node metastasis was revealed in 13 (12.6%) of 103 patients. All metastatic lymph nodes were identified within SNs. SNs of these 13 patients had positive findings on RT-PCR. Twenty-eight (27.2%) of 103 patients had negative histopathology but positive findings on RT-PCR. In 7 patients (6.8%), SNs were negative but NSNs were positive on RT-PCR. RT-PCR-positive NSNs were present in the same station as corresponding SNs in 3 of these 7 patients and in the same basin as SNs in 4 patients.

The real-time multiplex RT-PCR assay is a useful tool for the detection of MM in SNs and NSNs in patients with gastric cancer.