Thyroid nodule with Hashimoto thyroiditis in childhood - a challenging experience.

Fine-needle aspiration biopsy (FNAB) of the thyroid, although not perfect, is considered currently the best preoperative method in establishing malignancy in a thyroid nodule. We report the case of an 8-year-old girl with a thyroid mass in the right thyroid lobe. Endocrine investigations revealed subclinical hypothyroidism and high titer of anti-thyroid peroxidase antibodies. Fine Needle Aspiration Biopsy (FNAB) of the right side of the thyroid gland, where on thyroid ultrasonography (US) a poorly defined iso-/hypoechoic nodule with irregular margins was detected, revealed a background of lymphocytes and plasma cells mixed with follicular cells with reactive changes. After four months of treatment with L-thyroxine, ultrasonographic follow up showed an increase in nodule size. FNAB was performed again but showed non-diagnostic cytology. Right lobectomy was performed and the pathology report shows papillary carcinoma, follicular variant predominantly with components of insular growth. We discuss the false-negative FNAB interpretation because of the concomitant autoimmune thyroiditis. Management strategy for this case and the prognosis is also discussed.