Poorly differentiated thyroid carcinoma arising from a lithium-induced goiter in a patient with schizophrenia: a case report

Background Lithium use causes goiter by increasing serum thyroid-stimulating hormone levels through the inhibition of thyroid hormone release. However, there are no reports of poorly differentiated thyroid carcinoma resulting from lithium-induced goiter. Herein, we report the case of a patient with schizophrenia who developed poorly differentiated thyroid carcinoma arising from a lithium-induced goiter. Case presentation A 61-year-old woman who was taking lithium for schizophrenia, visited the thyroid-endocrine center with a 10 × 12 cm anterior neck mass. She had a slowly growing goiter approximately 30 years ago; however, when she came to the hospital for diabetes diagnosis 2 years ago, she had no accompanying symptoms and refused evaluation. Three months before her visit, her dysphagia and dyspnea worsened as the size of her goiter increased rapidly. A neck ultrasound and enhanced thyroid computed tomography (CT) examination revealed a 10.9 × 9.2 × 12.8 cm size multi-lobulated mass on the right thyroid gland, leading to a leftward deviation of the trachea. Diagnostic total thyroidectomy was performed, and microscopic findings and immunohistochemical staining results indicated poorly differentiated thyroid carcinoma (PDTC) in the right thyroid mass. Mutation analyses for BRAF and the telomerase reverse transcriptase (TERT) promoter was performed. No BRAF gene mutations were detected; however, TERT promoter C228T point mutation was present in the PDTC. The patient underwent radioactive iodine therapy two months after the surgery. At a recent follow-up 4 months postoperatively, she was taking thyroid hormone replacement and remained in a relatively good health with a serum thyroglobulin level of 0.55 ng/ml. Conclusions Thyroid examination of psychiatric patients who develop goiter due to long-term lithium treatment should be monitored regularly, and appropriate investigations and surgery should be performed in a timely manner if the goiter is growing rapidly.