THU674 Papillary Thyroid Carcinoma Presenting As A Benign Ectopic Thyroid Mass In The Anterior Mediastinum. A Case Report

Disclosure: M.V. David-santos: None. C. Narvacan-montano: None. Background: Ectopic Thyroid Tissue (ETT) is a rare developmental anomaly that is due to the failure of the thyroid gland to assume its position in front of the trachea. Ectopic Thyroid tissue in the mediastinum is very rare, with only a few cases reported in the literature. An incidental Papillary Thyroid Carcinoma presenting as a mediastinal mass that turns out to be benign ectopic thyroid cells is even rarer. Case: This is the case of a 33-year-old female who presented with sudden onset difficulty of breathing and chest heaviness. On workup, she was found to have an anterior mediastinal mass, which showed ectopic thyroid cells on biopsy. Further evaluation of the neck area revealed a 1.25 cm x 1 x 1.13 cm nodule on the thyroid gland which showed suspicious for Papillary Thyroid Carcinoma on Fine needle aspiration biopsy. The patient underwent Total Thyroidectomy and Excision of the Anterior Mediastinal Mass. The histopathologic report of the thyroid mass revealed a Conventional Unifocal Papillary Thyroid Carcinoma, while the excised tissues comprising the mediastinal mass were consistent with benign ectopic thyroid tissues with colloid goiter. Conclusion: The presence of the ectopic thyroid mass in the anterior mediastinum may be a potential area for metastasis. The final pathologic report nevertheless, categorizes this Papillary thyroid carcinoma as having a low risk of metastasis as per the American Thyroid Association Classification of 2015. Hence the conservative approach of Suppression therapy and active surveillance is the choice of management for this unusual case. Presentation: Thursday, June 15, 2023