Role of serum thyroglobulin in the pre-operative evaluation of follicular thyroid tumours.

AIMS: There is no reliable diagnostic test for pre-operative differentiation between benign and malignant follicular and Hurthle cell neoplasms. Measurements of serum thyroglobulin (Tg) are currently only used post-operatively as a marker of recurrent disease or distant metastases in the follow-up of patient with differentiated thyroid cancer. In this study pre-operative serum Tg measurements were performed with the aim of investigating whether Tg levels differ in benign and malignant follicular and Hurthle cell neoplasms.
METHODS: In 516 patients who underwent thyroid surgery at the Institute of Oncology in Ljubljana, Slovenia, from 1990 to 1996, serum Tg concentration was measured in addition to the standard pre-operative tests (fine-needle aspiration biopsy, ultrasonography, 99mTc scanning and hormonal profile). After the operation, patients were divided into 11 groups based on their histological diagnosis (papillary cancer--classic, papillary cancer--follicular variant, papillary cancer oncocytic variant, occult papillary cancer, follicular adenoma, follicular cancer, Hurthle cell adenoma, Hurthle cell cancer, anaplastic cancer, medullary cancer, nodular goiter) and the serum Tg values of the different groups were compared.
RESULTS: In groups of patients with follicular and Hurthle cell cancer, median Tg values were higher (2895 and 638.5 ng/ml) and, statistically, differed significantly from the serum Tg values in all other groups (P<0.01). Sensitivities and specificities of the tests were 71.8% and 80.4% for follicular cancer and 55.6% and 83.8% for Hurthle cell cancer, while positive and negative predictive values were 75.6% and 77.1% for follicular cancer and 75% and 68.4% for Hurthle cell cancer.
CONCLUSIONS: These results indicate that pre-operative serum Tg measurements might be an important additional diagnostic tool in the pre-operative work-up of patients with thyroid tumours.