Concurrent Papillary Carcinoma of Thyroglossal Duct Cyst and Thyroid Isthmus, Beyond the Sistrunk Procedure

Introduction/Background: Papillary carcinoma (PC) originating from the thyroglossal cyst is a rare entity. It is even more uncommon to have concurrent thyroglossal duct cyst PC and papillary thyroid carcinomas (PTC). The surgical approach for such patients would involve a combination of a Sistrunk’s procedure and total thyroidectomy. We describe management of a patient found to have multi focal PC originating from a thyroglossal duct cyst and thyroid isthmus with extensive cervical lymph node metastasis. Clinical Case: 30-year-old male presented to PCP with palpable bilateral cervical adenopathy most prominent in the right supraclavicular region. Neck ultrasound confirmed multiple metastatic appearing nodes (largest 4cm) in the central, right and left lateral cervical compartments as well as a hypoechoic, TI-RADS category 5 right thyroid isthmus nodule. FNA of the cervical nodes confirmed metastatic PTC. Neck CT in addition to extensive cervical adenopathy revealed a 2 cm solid mass inferior to the central hyoid bone with infiltrative borders and calcifications suspicious for a primary tumor. Patient underwent total thyroidectomy with central compartment lymph node dissection, excision of thyroglossal cyst and bilateral modified radical neck dissections. Histopathology report revealed a 2.4 cm thyroglossal duct tumor and a 1.1 cm tumor in the thyroid isthmus, confirming two separate tumors both being classical variants of papillary thyroid carcinoma, with no lympho-vascular invasion and 8/53 positive lymph nodes. BRAF V600E mutation was positive. On follow up, the patient is doing well and has deferred adjuvant radioactive iodine treatment for 6 months for personal reasons. Clinical Lesson/ Conclusion: PC of the thyroglossal cyst with synchronous isthmic PTC merits total thyroidectomy and central compartment dissection in addition to the Sistrunk’s procedure, as the likelihood of local metastasis is high. Presence of BRAF V600E mutation has been identified as a predictor of more aggressive behavior in isolated PC of the thyroglossal duct cyst, suggesting a need for more than a Sistrunk’s procedure in such patients. Our patient, who presented with local lymph node metastasis supports this conclusion. Determining BRAF mutation status preoperatively may be a helpful strategy in planning the extent of surgery. Keywords Thyroglossal duct cyst, Papillary thyroid carcinoma, BRAF mutation