Lymph Nodes

The proportion of patients who relapse from tumors of all types suggests that many patients are understaged and that better methods are needed to detect nodal metastasis. Tumor cells in lymph nodes can be detected by RT-PCR, and cases of histologically negative nodes that are molec-ularly positive are not uncommon. There is little question that molecular testing can increase the sensitivity of occult tumor cell detection. However, the clinical significance of detecting occult tumor cells has not been fully clarified. Several studies demonstrating a relationship between a positive molecular result for lymph nodes and patient outcome have been reported,29,41,47,48 while others have shown no relationship. Many factors contribute to these confusing results, including variations in the assays (differing targets, variable sensitivity and specificity) and the amount of lymph node sampled (small metastatic foci may be missed). Additionally, the clinical relevance of tiny micrometastatic nodal metastases, even those evident by histology, remains in question.49,50

With the availability of rapid-cycle PCR technology, the application of molecular methods to the intraoperative assessment of patient samples has been proposed. In patients undergoing esophageal resection, RT-PCR has been used to detect CEA transcripts in lymph nodes during surgery and has revealed molecularly positive nodes that are histologically negative. In this small series, the positive patient suffered an earlier recurrence of cancer than those who were RT-PCR negative.51

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