TG and cancer: Thyroglobulin (Tg) is a glycoprotein specific to differentiated thyroid tissue; after thyroidectomy and radioiodine remnant ablation, an elevated serum Tg level is a sensitive marker of residual cancer.3 Periodical measurement of Tg after initial thyroid ablative therapy is recommended in the monitoring of PTC patients.4 Nevertheless, Tg level may be affected by the various laboratory assays used.5 Interference may also occur in the presence of anti-Tg antibodies or heterophile antibodies.6,7