RESUMO
Background/Objective: Occult papillary thyroid carcinoma (PTC) is PTC with metastasis but without identification of primary thyroid cancer on preoperative ultrasonography. Published reports on occult PTC in children are limited. Case Report: We describe a 16-year-old female with occult PTC who initially presented with a painless left sided cystic neck mass. Diffuse sclerosing variant papillary thyroid cancer was found in the resected neck mass and thyroid ultrasound did not show any nodules or features of carcinoma. After total thyroidectomy, pathological examination of the thyroid revealed papillary thyroid microcarcinoma. Discussion: We describe a rare case of occult diffuse sclerosing variant papillary thyroid cancer presenting as a cystic neck mass mimicking a second branchial cleft cyst in an adolescent patient. When metastatic PTC is found without evidence of nodule on thyroid imaging, occult PTC of the thyroid is the likely diagnosis. Conclusion: Total thyroidectomy ± neck dissection followed by TSH suppression and radioactive iodine therapy remains the appropriate diagnostic and therapeutic interventions.