[A case of tumor progression after gamma knife radiosurgery for brain metastasis of thyroid papillary carcinoma in deep subcortical white matter].

We report a case of a brain metastasis of thyroid papillary carcinoma. A 67-year-old man had undergone a radical operation for thyroid papillary carcinoma 6 years before. He had no neurological deficit, but CT showed an enhanced lesion in the left frontal lobe. He underwent gamma knife radiosurgery. Four months later, the lesion with massive peritumoral edema was identified on magnetic resonance imaging (MRI). The edema was treated medically, however, recovery was seen neither on MRI nor clinically. Then left craniotomy was performed, with total resection of the tumor. During the operation Komai's stereotactic instruments were used for CT guided stereotactic surgery. Histopathological analysis of the surgical specimen confirmed mixed necrosis and papillary carcinoma of the thyroid gland. The patient was discharged without neurological deficit and is now kept under observation as an outpatient. Brain metastases from thyroid cancer are rare and we report a case of resection of brain metastasis of a thyroid papillary carcinoma after gamma knife radiosurgery.