Focused examination of sentinel lymph nodes upstages early colorectal carcinoma

Approximately 30 per cent of patients with early colorectal carcinoma (CRC) develop systemic disease. A subgroup of these patients may harbor occult micrometastatic disease and might benefit from adjuvant chemotherapy. We investigated sentinel lymph node (SLN) mapping and focused pathologic examination of the SLN as a means of detecting nodal micrometastases. Between 1996 and 2000 SLN mapping was performed in 50 consecutive patients undergoing colectomy for CRC. All lymph nodes in the resection specimen were examined via routine hematoxylin and eosin (H&E) staining. In addition multiple sections of each SLN were examined via both H&E and cytokeratin immunohistochemistry. At least one SLN was identified in 47 patients (94%). In seven patients (14%) SLN mapping identified aberrant drainage that altered the planned resection. The SLN(s) correctly predicted nodal basin status in 44 of 47 (94%) cases; there were three falsely negative SLNs. Sixteen cases had positive SLNs by conventional H&E staining. An additional 10 (20%) cases were upstaged by a focused examination of the SLNs. Micrometastases were identified in three cases by H&E staining of multiple sections of the SLN and in seven only by cytokeratin immunohistochemistry. In nine cases the SLN was the only node containing tumor cells. In this study, SLN mapping demonstrated aberrant nodal drainage patterns that altered the surgical resection in patients with CRC. Focused examination of SLNs may detect micrometastases missed by conventional techniques and thereby identify patients who might benefit from adjuvant therapy.