A Case of Sudden Diffuse Thyroid Swelling after Fine Needle Aspiration Cytology where Changes over Time Were Confirmed by Ultrasonography

We encountered a case of diffuse thyroid swelling after fine needle aspiration (dTSaFNA) cytology, and monitored the swelling by thyroid ultrasonography. The scan findings are reported. A 57-year-old female visited our hospital complaining of swelling in her anterior neck. She had a history of metal allergy and was not taking any medications. Because a solid cystic tumor was detected in the left thyroid lobe, we decided to perform fine-needle aspiration cytology (FNAC). When the second aspiration was performed with a 22G needle inserted into the nodule in the left lobe, the patient immediately complained of pain in her neck. Within 2 minutes, her anterior neck swelled up and ultrasonography showed vascular dilatation in the left thyroid lobe. Neck cooling with steroid injection was undertaken. However, over the next 5 minutes, the vascular dilatation also spread to the right lobe. About 15 minutes later, the vessels gradually became unclear, and the neck pain and swelling persisted, and the patient was hospitalized for observation. By the following day, all the symptoms and signs had resolved and the patient was discharged. FNA is associated with the risk of neck swelling caused by hemorrhage or dTSaFNA. To make a prompt diagnosis and provide appropriate treatment for this complication, ultrasonography could be useful.