A Prospective Evaluation of Radiocolloid and Immunohistochemical Staining in Colon Carcinoma Lymphatic Mapping

BACKGROUND. Although the utility of lymphatic mapping (LM) and sentinel lymph node (SLN) biopsy in patients with melanoma and breast carcinoma has been well documented, this same is not true for patients with colon carcinoma. The authors previously reported a high false-negative rate for SLN biopsy in patients with colon carcinoma using isosulfan blue dye alone. The objective of the current study was to determine whether radiocolloid would increase the sensitivity of LM/SLN biopsy in patients with colon carcinoma. METHODS. The authors performed LM on 57 patients with colon carcinoma using both isosulfan blue dye and radiocolloid. The SLN(s) were identified by either their blue color or by increased radioactivity. The SLNs then underwent both routine histologic sectioning and immunohistochemical (IHC) staining for cytokeratins. RESULTS. An SLN was identified in 56 patients (98%). Radiocolloid was able to identify only 1 additional positive SLN (9%). Overall, it was found that the disease had metastasized to the lymph nodes in 22 patients, even though there was no evidence of disease in the SLN(s) in 11 of those 22 patients on routine histologic sectioning (false-negative rate, 50%; sensitivity, 50%). In five patients, IHC of the SLN was the only indicator of metastatic disease. The inclusion of IHC-positive SLNs in these calculations would decrease the false-negative rate to 17% and would increase the sensitivity of SLN biopsy to 83%. CONCLUSIONS. In the current study, the addition of radiocolloid did not increase the sensitivity of detection of positive SLN(s) compared with the use of isosulfan blue dye alone. IHC of the SLN potentially may increase the sensitivity of LM and reduce the false-negative rate. However, the long-term prognostic significance of IHC in patients with colon carcinoma remains controversial.