Nonshadowing echogenic foci in thyroid nodules: are certain appearances enough to avoid thyroid biopsy?

The purpose of this study was to further classify nonshadowing echogenic foci and examine the association with malignancy.

This study received Institutional Review Board approval and was Health Insurance Portability and Accountability Act compliant. A total of 371 consecutive thyroid nodules were evaluated in 189 patients (177 female and 12 male; mean age, 59 years; range, 21-92 years). Eighty-six nodules (23%) measured 5 mm or larger and contained nonshadowing echogenic foci with a mean nodule diameter of 16 mm (5-66 mm). Blinded review of these nodules 12 months later was performed. Echogenic foci were classified as follows: showing a comet tail artifact (type 1), linear and brightly echogenic (type 2), round and indeterminate (type 3), and microcalcifications (type 4). All available thyroid sonograms and pathologic data were then reviewed.

Nineteen nodules (22%) showed a classic comet tail artifact, with malignancy in 0 of 19. Six (32%) had negative pathologic results, and 9 (47%) had stable imaging follow-up (mean, 37 months). Twenty-nine nodules (34%) showed linear and brightly echogenic foci, with malignancy in 0 of 29. Fifteen (52%) had negative pathologic results, and 11 (38%) had stable imaging follow-up (mean, 34 months). Twenty-four nodules (28%) showed round and indeterminate echogenic foci, with 1 of 24 (4%) containing papillary carcinoma. Thirteen (54%) had negative pathologic results, and 8 (33%) had stable imaging follow-up (mean, 24 months). Fourteen nodules (16%) contained microcalcifications, with 4 of 14 (29%) containing papillary thyroid cancer. Nine (64%) had negative pathologic results, and 1 (7%) had stable imaging follow-up (63 months).

Nonshadowing brightly echogenic linear foci with or without a comet tail artifact may be a benign finding. Confirmatory studies are needed for this result to be applied clinically.