Monday, April 4, 2011

Pediatric Thyroid Cancer: Causes

Thyroid carcinoma is a known sequela of radiation exposure. From the 1920s to the 1960s, external beam radiation was used for treatment of benign lesions (eg, tinea capitis, tonsillar hypertrophy, acne, thymic enlargement, hemangiomas) prior to recognition of its carcinogenic effects.

The Chernobyl disaster in 1986 caused up to a 100-fold increase in the incidence of pediatric thyroid carcinoma in the exposed population. Cases associated with radiation exposure are mostly papillary carcinoma, and those associated iodine-deficient areas are more likely follicular.

Radiation and chemotherapy for other pediatric malignancies also have been implicated in thyroid malignancy. Children who undergo pretreatment radiation therapy prior to bone marrow transplant and children who undergo primary radiation treatments for Hodgkin lymphoma are at increased risk for thyroid cancer. The risk for thyroid cancer is dose dependent.

Congenital hypothyroidism (CH), due to either dyshormonogenesis or an iodine transporter defect, increases the risk of thyroid nodules. Chronic thyroid-stimulating hormone (TSH) elevation increases the risk of neoplastic transformation of thyroid. The benign nodules usually respond to thyroxine treatment. Those that remain or enlarge despite suppression therapy should undergo biopsy.

Thyroglossal duct cysts, the most common developmental thyroid anomaly, carry an increased, albeit small, risk of malignant transformation. This is one of the reasons excision with the Sistrunk procedure (removal of cyst, central hyoid bone, and core from the base of the tongue) is recommended. However, only 8 cases of malignant thyroglossal duct transformation have been reported in the literature.

Author: Mark E Gerber, MD, FACS, FAAP  Clinical Assistant Professor of Otolaryngology, University of Chicago, Pritzker School of Medicine; Section Head, Pediatric Otolaryngology-Head and Neck Surgery, NorthShore University HealthSystem 

Co-Author: Brian Kip Reilly, MD  Assistant Professor of Otolaryngology and Pediatrics, Department of Otolaryngology, Children's National Medical Center, George Washington University School of Medicine 

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