Treatment of recurrent thyroid cysts by injection of tetracycline or minocycline.

We analyzed the effects of tetracycline hydrochloride or minocycline hydrochloride sclerotherapy on 66 recurrent thyroid cysts. All were hemorrhagic lesions except one serous cyst; cytologic study showed all were benign. On average, three treatments were given until resolution or the patient became unavailable for follow-up. The cumulative frequency of cyst disappearance was 33%, 45%, 52%, and 59% after 1, 2, 3, and 4 treatments. Five additional patients had cyst resolution after six to 19 treatments, and the serous lesion did not resolve. Cysts requiring more than two treatments were larger at presentation than those resolving after one or two treatments. Side effects in 179 treatments were local pain lasting ten to 20 minutes in 4.5%, radiated pain lasting one to two hours in 4.5%, fatigue lasting one to two days in 3.9%, and a febrile sensation lasting one to two days in 2.8%. Hemorrhagic thyroid cysts can usually be cured by repeated tetracycline or minocycline sclerotherapy with tolerable side effects.