Papillary Thyroid Carcinoma within a Second Branchial Cleft Cyst. A Diagnostic and Treatment Challenge

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INTRODUCTION: Lateral cervical cystic masses are a relatively common occurrence in the otolaryngology practice, which are often attributed to second branchial cleft cysts. However, there should always be a high suspicion for malignancy until proven otherwise. CASE PRESENTATION: We present a clinical report of a lateral cervical cyst surgical excision where histopathological examination has revealed features of a branchial cleft cyst harboring a papillary thyroid carcinoma. This led to the clinically latent thyroid primary which was treated through thyroidectomy with selective neck dissection and radioactive iodine therapy. DISCUSSION: Across current literature regarding thyroid carcinomas arising within branchial cysts, primary thyroid carcinoma was identified in almost half the cases where thyroidectomy was performed. There is no established consensus on the decision of whether to perform a thyroidectomy in such cases, due to the paucity of data for similar cases. CONCLUSION: Although branchial cyst is a benign condition, it can harbor malignancy. When thyroid carcinoma occurs within such a cyst, without solid evidence of a thyroid primary, treating physicians are presented with a diagnostic and treatment dilemma. As more cases are discovered and reported, navigating this challenging dilemma will become clearer for the treating physicians.