Background. Metastatic disease in epithelial cancer results from tumor cell dissemination. We investigated an expression of cytokeratin 20 (CK20) by reverse transcriptase-polymerase chain reaction (RT-PCR) in differentiated (DTC) and anaplastic thyroid carcinomas (ATC) and correlated the results with TNM categories and the clinical follow-up. Methods. Tissue and blood samples of 32 patients with papillary (PTC), 17 patients with follicular (FTC), and 7 patients with ATC were obtained during operation and subjected to CK20 RT-PCR. Results. An expression of CK20 transcripts was detected in 47% of the tissue samples of PTC, 71% of the FTC, and 14% of the ATC. Patients with CK20-positive FTC had a significantly better outcome than patients with CK20-negative FTCs (P = .0016). Disseminated tumor cells were found in 9 of 22 (41%) blood samples of patients with CK20-positive carcinomas. The detection of CK20 transcripts in peripheral blood correlated with tumor categories. Four of 8 (50%) patients with DTC and circulating tumor cells developed local or distant recurrence compared with 3 of 13 (23%) patients with CK20-positive carcinomas and CK20-negative blood samples. Conclusion. Our results suggest that CK20 might be a suitable differentiation marker in thyroid carcinomas. In patients with CK20-positive tumors, those with CK20-posilive blood samples had a poorer prognosis. We suggest that patients with thyroid cancer with positive CK20 blood samples should be evaluated for further adjuvant therapies after surgery.
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