Pathologic examination of the sentinel lymph node in malignant melanoma

Sentinel lymphadenectomy is gaining increasing popularity in the staging an d treatment of patients with melanoma at risk for metastases. As a result, pathologists are encountering these specimens more frequently in their dail y practice. The pathologic status of the sentinel lymph node is pivotal to the patient's carl because it provides staging information that dictates th e need for further therapy, and therefore detailed pathologic assessment is warranted. A standard pathology protocol to handle these nodes has been de veloped at our institution and involves complete submission of all tissue w ith routine use of immunohistochemical staining for S-100 protein. By using this protocol, 838 sentinel lymph nodes from 357 patients have been examin ed, and metastases were found in 16% of patients. Although the metastasis w as clearly seen on sections stained with hematoxylin and eosin in 55% of th e positive patients, the immunostain showed metastatic disease not apprecia ble on initial hematoxylin and eosin screening in an additional 28 lymph no des (45% of node-positive patients). Intraoperative touch preparation cytol ogy may be used as an adjunct technique in sentinel lymph nodes grossly sus picious for metastatic disease. This technique has been performed on 23 sen tinel lymph nodes, with no false positives and an overall sensitivity of 62 %. The thorough pathologic evaluation of sentinel lymph nodes in patients w ith malignant melanoma requires complete submission of all tissue, routine use of immunohistochemistry, and touch preparation cytology in selected cas es.