Is minimal residual lymph node disease in papillary thyroid cancer of prognostic impact? An analysis of the epithelial cell adhesion molecule EpCAM in lymph nodes of 40 pN0 patients.

This study was aimed to assess the extend of nodal microdissemination in patients with pN0 papillary thyroid carcinoma (PTC) using immunohistochemical analysis. In early stage PTC both, systematic lymphadenectomy as well as radio iodine treatment, aimed to eliminate occult nodal tumor involvement, are under controversial debate, since little is known about the extend of lymphatic microdissemination in these patients. Formalin embedded samples of the resected lymph nodes were systematically screened for the presence of disseminated tumor cells using immunohistochemistry (monoclonal antibody Ber-EP4). Clinical and histopathological parameters as well as the post-operative course were recorded. Survival data were analysed by the Kaplan-Meier method and the log rank test. Overall 321 lymph nodes of 40 patients were screened immunohistochemically. In 12.5% of the patients disseminated occult tumor cells were diagnosed. In addition to tumor resection 90% of the patients underwent adjuvant radio-iodine treatment. The mean observation period in our collective was 72 months. The detection of disseminated tumor cells did not correlate with clinicopathologic risk parameters and did not have significant influence on the prognosis of these patients. Immunohistochemical analysis enables the detection of disseminated tumor cells in patients with pN0 PTC. This finding seems to support the application of adjuvant radio iodine, even in early tumor stages.