[Clinical significance of detecting lymph node micrometastasis of colorectal cancer by reverse transcriptase-polymerase chain reaction (RT-PCR)].

Background & Objective: It remains controversial whether lymph node micrometastasis has impact on staging and prognosis of colorectal cancer. This study was to compare the sensitivity of reverse transcriptase- polymerase chain reaction (RT-PCR) in detecting lymph node micrometastasis of colorectal cancer with pathological morphology and immunohistochemistry, and assess the impact of lymph node micrometastasis on clinical staging and prognosis of colorectal cancer.

Methods: Lymph nodes from 56 cases of colorectal cancer radical resection specimens were studied by RT-PCR to detect the expression of cytokeratin 20 (CK20) mRNA, and compared with routine pathology detection using hematoxylin and eosine (HE) staining, and immunohistochemistry using monoclonal antibody specifically against CK20. The patients had been followed up for 5 years.

Results: A total of 432 lymph nodes in 56 patients were analysed by pathological morphology, immunohistochemistry, and RT-PCR, the detected positive lymph node numbers were 247 (57.2%), 269 (62.3%), and 316 (73.1%), respectively. The difference in metastatic lymph node numbers was significant between pathological morphology and RT-PCR method (P< 0.05). Five-year disease- free survival rates of PN0,PN1, and PN2 stages detected by RT-PCR method were 100%, 61.9%, and 55.6%, respectively, significantly higher than those obtained by pathological morphology method, which were 80.0%, 60.0%, and 50.0%, respectively (P< 0.05).

Conclusions: Detecting lymph node micrometastasis of colorectal cancer with RT-PCR method is more sensitive than pathological morphology. RT-PCR method could define the TNM stage and make accurate prognosis for patients with colorectal cancer.