Association between the HLA-G molecule and lymph node metastasis in papillary thyroid cancer.

Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer and can present as lymph node metastasis in 30 to 65% of cases when initially diagnosed. High frequency recurrence, distant metastasis and treatment resistance can be found in cases of PTC so early diagnosis and treatment are critical for improved prognosis and better survival rates. The characterization of new biomarkers has proved useful for the diagnosis and follow-up of these patients. HLA-G is a non-classical HLA class I molecule whose expression in cancer cells has been associated with tumor evasion of immune response. Therefore, the aim of this study was to investigate the HLA-G expression and its clinical significance in PTC. Paraffin-embedded thyroid biopsies of 70 PTC patients (40 of whom had presented with metastasis) were evaluated. HLA-G-staining was observed in tumor cells in PTC, and the HLA-G expression was significantly associated with an increased occurrence of lymph node metastasis (p=0.0006) and capsular invasion (p=0.02). This preliminary data shows the HLA-G expression in thyroid carcinoma specimens for the first time and suggests that this expression could impair efficient anti-tumor immunity in PTC. This would indicate that HLA-G could have an independent prognostic value in PTC, principally for tumor recurrence.