甲状腺に原発巣のない頸部リンパ節3つに発生した潜在性甲状腺癌：症例報告

Occult thyroid carcinoma (OTC) involves cervical lymph node metastases without primary papillary thyroid carcinoma (PTC). A 57-year-old man presented with a left neck mass. Ultrasonography (US) revealed a mass in the left cervical node (inferior internal jugular node, Level IV). Positron emission tomography/computed tomography (PET/CT) and fine needle aspiration biopsy indicated suspected PTC metastasis. The serum thyroglobulin (Tg) level was elevated. Total thyroidectomy and bilateral central neck and left cervical dissection revealed no thyroid carcinoma, while the left cervical node showed ground glass nuclei and proliferation. Our diagnosis was PTC with no primary origin, pT0N1bM0 Stage II. Due to a low risk of recurrence, we initiated thyroid-stimulating hormone (TSH) suppression therapy. Tg levels remained low 4 years postoperatively with no signs of recurrence. The optimal management of OTC cases remains unclear and blood tests (Tg levels), risk of recurrence, and patient characteristics must be considered.