RT-PCR and immunohistochemical evaluation of sentinel lymph nodes after in vivo mapping with Patent Blue V in colon cancer patients

Objective. Lymph node status is the most important predictive factor in the treatment of colorectal cancer. As sentinel lymph node ( SLN) biopsy might upstage stage II colon cancer, it could have therapeutic consequences in the future. We investigated the feasibility of in vivo SLN detection with Patent Blue V dye and evaluated nodal microstaging and ultrastaging using cytokeratin immunohistochemistry and reverse transcriptase-polymerase chain reaction ( RTPCR). Material and methods. In 30 consecutive patients operated on for colon cancer, subserosal injection with Patent Blue dye was used for SLN detection in four different hospitals under the supervision of one regional coordinator. In searching for occult micrometastases, each SLN was examined at three levels. In tumor-negative SLNs at routine hematoxylin-eosin ( H&E) examination ( pN0) we performed CK8/CK18 immunohistochemistry ( IHC) and RT-PCR for carcinoembryonic antigen ( CEA). Results. The procedure was successful in 29 out of 30 patients ( 97%). The SLN was negative in 18 patients detected by H&E and IHC. In 16 patients the non-SLN was also negative, leading to a negative predictive value of 89% and an accuracy of 93%. Upstaging occurred in 10 patients ( 33%) - 7 by IHC and 3 by RT-PCR. Aberrant lymphatic drainage was seen in 3 patients ( 10%). Conclusions. The SLN concept in colon carcinoma using Patent Blue V is feasible and accurate. It leads to upstaging of nodal status in 33% of patients when IHC and PCR techniques are combined. Therefore, the clinical value of SLN should be the subject of further studies.