Intraoperative imprint cytology for evaluation of sentinel lymph nodes from visceral malignancies

Although originally described for breast cancer and melanoma, sentinel lymph node (SLN) mapping techniques are being investigated in the treatment of visceral malignancies. There is no literature evaluating intraoperative analysis of SLNs from visceral sites. We evaluated the utility of touch preparation intraoperative imprint cytology (IIC) in evaluating SLNs harvested in the setting of visceral malignancy. SLN mapping procedures involving 50 cases of visceral malignancy (37 colon, 12 gastric, and 1 small bowel), from February 1999 through August 2001, were studied. In each case, subserosal injections of isosulfan blue were used to identify the SLN. The SLNs were then sent fresh to the pathology laboratory for evaluation by IIC. A standard lymphadenectomy was performed in all cases. Postoperatively, the SLNs were evaluated by means of using hematoxylin and eosin staining. If these stains were normal, immunohistochemical analyses using carcinoembryonic antigen and cytokeratin were subsequently performed. SLNs were successfully identified in 46 cases (92%), and a total of 95 SLNs were harvested. The average number of SLNs was 1.9 with a range of one to six. More SLNs were found with gastric than with colonic lesions (2.8 vs. 1.8; P=.017). Evaluable IIC in 41 cases revealed metastatic disease in 10 SLNs, representing seven patients. Of the 34 patients with normal IIC, five were found to have positive SLNs on hematoxylin and eosin staining. An additional three patients were found to have positive SLNs only on immunohistochemical analysis. The overall sensitivity and specificity of IIC was 64% and 100%, respectively. This resulted in a positive predictive value of 100% and a negative predictive value of 86%. The use of IIC to evaluate SLNs from visceral malignancies is clearly feasible. When the IIC of the SLN is positive, the surgeon may feel confident that disease is actually present in the SLN. If there is a negative result, the technique may miss disease that is present on subsequent permanent sections. We do not recommend routine use of IIC; however, it may be of use in clinical trials.