Clinical significance of the comet-tail artifact in thyroid ultrasound.

The comet-tail artifact is commonly encountered in a variety of clinical conditions; however, its presence and significance in a thyroid nodule has not been documented before. We document its presence in 100 patients who underwent ultrasound examinations of the neck and thyroid. None of the thyroid nodules showed any evidence of malignancy on repeated fine-needle aspiration cytology (FNAC). In 85% of patients with the artifact, abundant colloid was seen on FNAC, suggesting that the artifact may be related to the presence of colloid. Four different patterns of distribution of the artifact within the nodule were noted and these helped to determine the size of the needle to be used for a successful aspiration.