Primary papillary carcinoma arising from median ectopic thyroid in multinodular goitre

Abstract

CARCINOMA ARISING from thyroglossal duct remnants is a rare entity [ 11. An interesting case of papillary thyroid carcinoma of the thyroglossal duct remnants, observed among 700 patients with thyroid carcinoma, is here reported and its particular features described. A 66-year-old woman, with a lo-year history of multinodular goitre, noticed a progressively growing mass in the midline of her neck 12 months ago. She had been in suppressive thyroid therapy for the last 7 years (L-thyroxine 2 pg/kg body weight resulting in suppressed thyroid stimulating hormone (TSH) response to thyrotropin releasing hormone (TRH). Free and total T4 and T3 were within normal range and TSH levels were undetectable. No uptake was detected over the midline neck mass in the 13tI thyroid scan, in which the thyroid gland appeared enlarged with a dishomogeneous distribution of the tracer. Ultrasonography revealed a diffuse enlargement of the thyroid gland, with mixed lesions and, above the gland, a solid lesion 2.0 cm in diameter with calcification. Cytopathological examination of the neck mass suggested a papillary proliferation. At surgery, a mass of diameter 2.2 cm just below the hyoid bone, was removed and a total thyroidectomy was performed. The mass was 3 cm above the upper margin of the thyroid gland and so was unconnected to it. Histological examination confirmed the presence of papillary carcinoma in the mass, whereas no evidence of neoplasm resulted in the thyroid gland. The interesting aspect of this case is the inability of the continuous, prolonged administration of thyroid hormone in protecting the patient from the occurrence of cancer. The case reported seems to contradict the belief that the growth of papillary carcinoma depends solely on TSH stimulation. This view stems from at least two kinds of observations: (i) that thyroid hyperplasia associated with elevated TSH levels in congenital goitrous patients untreated for many years can lead to malignant degeneration [2] and (ii) that differentiated tumours can show normal TSH receptors. This fact can explain their TSH dependent growth, whereas anaplastic cancer lacks high-affinity receptors and shows TSH-independent growth [3]. In conclusion the case described is consistent with a rare neoplastic localisation in the thyroglossal duct remnants and supports the possible+ven though unusual-development of cancer during suppressive therapy.