Clinical presentation: A 51-year-old man was referred for evaluation of a thyroid nodule discovered by the patient himself.

Palpation: a firm nodule in the right lobe.

Result of blood test: TSH 1.20 mIU/L.

Ultrasonography. The thyroid was echonormal. A large cystic nodule occupied almost the entire right lobe. The nodule had echonormal solid parts. The type of the cyst was doubtful before aspiration of 14 mL brown fluid, however thereafter it became evident that this is a central-type cystic nodule.

Aspiration cytology resulted in non-diagnostic cystic lesion.

Suggestion: repeat ultrasound in a year, if the cyst refills than sooner.

Comments.

1. The echogenicity of a relatively large solid part of a cystic lesion frequently changes after aspiration. I am not aware of any publications related to this issue. It seems better to determine the echogenicity of the solid part after the aspiration, otherwise the amplification of the echo signal may get increase the echogenicity of the solid portion.
   
2. After the removal of the cystic content, the borders of the nodule became irregular. This is a frequent finding in cystic nodules.