[Detection of micrometastases of colorectal carcinoma in lymph nodes]

Dissemination of lymph nodes is a known prognostic factor in colorectal carcinoma. Micrometastases in lymph nodes can be missed when studied by routine techniques. We analyzed 162 lymph nodes from 30 patients with colonic carcinoma and using routine techniques, they were classified as follows: two Dukes A; nineteen Dukes B; and nine Dukes C. A patient with benign colon disease served as negative control. Lymph nodes were all sectioned in halves, with one of the halves stored in liquid nitrogen for molecular biology examination by carcinoembryonic antigen expression. The other formalin-fixed and paraffin embedded halves were saved for both pathologic and immunohistochemical examination. For Dukes A and Dukes B tumors, reverse transcriptase-polymerase chain reaction (RT-PCR) had a 50% higher sensitivity in the detection of micrometastases. The expression of carcinoembryonic antigen (CEA) was detected in all Dukes C cases, which were considered as positive controls. These results showed that RT-PCR has a higher sensitivity in the detection of micrometastases than routine techniques, including immunohistochemistry.