Thyroid carcinoma is the most common endocrine malignancy. Approximately 90% of non-medullary thyroid malignancies are classified as well-differentiated thyroid carcinomas. Even though this type of tumor is not aggressive and usually curable after therapy, recurrence develops in 20-40% and progression to cellular de-differentiation occurs in up to 30% of patients. Poorly differentiated cancers are characterized by loss of thyroid-specific functions and properties, such as the capacity to concentrate radioiodide. Therapeutic options for de-differentiated thyroid cancer are limited and generally not efficient. Recent studies with retinoic acid (RA) have shown that this drug can induce re-differentiation of the thyrocyte in vitro, as suggested by increased expression of thyroglobulin, type I iodothyronine 5'-deiodinase and the sodium/iodide symporter, and by the increment of cellular iodide uptake. Clinical research demonstrated beneficial effects of RA, with 40% of patients with radioiodine non-responsive tumor showing increase of iodide uptake and 20% tumor regression, after RA treatment.
Retinoic acid; Isotretinoin; Thyroid carcinoma; De-differentiation; Re-differentiation
