Resolution of recurrent thyroid cysts with tetracycline instillation.

Nine patients with recurrent purely cystic thyroid nodules after one or two previous cyst aspirations were treated with repeat cyst aspiration and instillation of intracystic tetracycline hydrochloride. All but two of the patients' cysts resolved completely and have not recurred after a follow-up period of 12 to 50 months (mean = 40). The remaining patients had a partial response that left them with clinically insignificant lesions. The procedure was well tolerated and obviated the need for further therapy in all patients. Cyst aspiration and tetracycline instillation is a safe and effective treatment of recurrent purely cystic thyroid nodules that eliminates the need for surgical excision.