[Lymph node micrometastases in colorectal cancer].

Lymph node (LN) micrometastases in colorectal cancer (CRC) has been discussed for a long time. Previous reports showed that micrometastases detected by immunohistochemistry (IHC) appeared to have no clinical impact, but that occult disease detected by molecular techniques such as RT-PCR might be associated with poor prognosis. At present, several factors are proposed as high risks for disease recurrence of stage II CRC, including T4 invasiveness, vascular invasion, poorly differentiated adenocarcinoma or mucinous carcinoma, tumor budding, wall perforation, and insufficient assessment of dissected LNs. However, it was reported that 75% of 24,847 stage II CRC patients retained specific risk factors, and the efficacy of chemotherapy in such patients has not been confirmed. A recent meta-analysis by Weitz et al. has concluded that occult disease was significantly associated with poor prognosis of node-negative CRC, irrespective of the detection method, i.e., IHC or RT-PCR. For efficient selection of high-risk stage II CRC patients, a prospective, large-scale clinical trial is essential using a convenient, simple molecular modality such as the one-step nucleic acid amplification assay.