Inspissated colloid

Inspissated colloid (colloid crystals) in a thyroid nodule leads to focal hyperechogenic foci, which can potentially be confused with microcalcifications.

Radiographic features

Ultrasound

• hyperechoic focus in a thyroid nodule
• reverberation artifact / comet-tail artifact
  • this feature is the most reliable in differentiating inspissated colloid from microcalcifications

Inspissated colloid can vary in size and tend to be larger than microcalcifications, however, there is overlap in size between the two entities.

Treatment and prognosis

Differentiation between inspissated colloid and microcalcifications in a thyroid nodule is important. Inspissated colloid is not associated with malignancy and fine needle aspiration (FNA) is unnecessary. Microcalcifications are associated with papillary thyroid cancer and FNA is almost always indicated for nodules with microcalcifications.