FNAC of thyroid cyst:

 
This was a large cystic lesion of the right lobe of thyroid. Ultrasound guided fine needle aspiration of the cyst helped to drain the contents of the cyst as well as to ascertain the nature of the cyst contents. Ultrasound guided aspiration done here shows the needle tip descending into the cyst (seen as the bright mobile echogenic focus in the cyst lumen). The ultrasound probe (here) is placed perpendicular to the long axis of the needle- resulting in the needle tip being visualized. If the needle's long axis is parallel to the ultrasound beam (and the ultrasound probe), a linear echo of the needle can be visualized.
See: http://radiographics.rsna.org/content/28/7/1869.full