術前に甲状腺癌リンパ節転移との鑑別が困難であった頸部神経鞘腫の１例

A female patient in her 60s visited her previous doctor because of a right cervical mass that exist for 7 years and gradually increased in size. As she was suspected of cervical lymph node metastasis of thyroid cancer, she was referred to our hospital. At the initial visit, a 5-cm right cervical mass and enlargement of the right lobe of the thyroid gland were observed. Fine needle aspiration cytology was performed on both, but no malignant findings were observed. To confirm the diagnosis and improve the patient’s appearance, a right lobectomy of the thyroid gland and resection of the right cervical mass were performed. A rapid intraoperative histological examination of the cervical mass revealed a schwannoma. The right thyroid tumor was diagnosed as follicular adenoma. Her postoperative course was good, and after several years of follow-up, patient consultation was terminated.
Neurolemmoma is a benign tumor arising from Schwann cells in the nerve sheath, and it occurs frequently throughout the head and neck region, with 25%-45% of cases occurring in this region. Cervical schwannomas are characterized by irritation of the vagus nerve, brachial plexus, and sympathetic nerves. However, many patients present with only a painless neck mass, as in this case. Although the mass can be diagnosed by puncture aspiration cytology in some cases, sufficient specimens are often unavailable, and the diagnosis is made preoperatively in about half of all cases.
Differential diagnoses of an anterior cervical mass include malignant lymphoma, cervical lymph node metastases of malignant tumors, submandibular gland tumors, and tuberculous lymph node metastases. In this patient, we also considered lymph node metastasis of thyroid cancer. However, a histological examination did not detect malignancy in either the thyroid gland or neck mass, and we considered that the thyroid follicular adenoma and the cervical schwannoma occurred independently.
We report our experience of cervical schwannoma combined with thyroid tumor which was suspected of lymph node metastasis of thyroid cancer.