Inspissated colloid and microcalcifications in a thyroid nodule can sometimes be confused on ultrasound. Reverberation artifact ("comet-tail artifact") can be useful to help make the diagnosis of inspissated colloid. Unlike microcalcifications, inspissated colloid does not confer increased malignancy risk to a thyroid nodule.

These foci were originally called microcalcifications and the nodules were biopsied. There was no malignancy on the biopsies.

The differences between small foci of inspissated colloid and microcalcifications can be subtle on ultrasound when the echogenic foci are small. One should look closely for the reverberation artifact to potentially avoid biopsy in a patient who would not need it.