Sonographic-Pathologic Correlation for Punctate Echogenic Reflectors in Papillary Thyroid Carcinoma: What Are They?

It is commonly held that punctate nonshadowing echogenic foci on sonography, often termed microcalcifications, represent psammoma bodies. We aimed to determine the validity of this supposition by correlating the presence of punctate echogenic foci on sonography with their presence at histopathologic examination. We examined 51 nodules (surgically proven papillary thyroid carcinoma) by sonography and histopathologic examination. On the latter, nodules were examined for evidence of psammomatous calcifications, dystrophic calcifications, and colloid. Two subspecialty-trained radiologists with 2 and 25 years of experience in sonography, respectively, reviewed the sonograms for the presence and distribution of punctate echogenic foci. All nodules contained colloid at histologic examination. Twenty of the papillary carcinomas lacked any calcification at pathologic examination. In the remaining 31 nodules with calcifications, 13 had psammomatous calcifications only; 6 had both coarse and psammomatous calcifications; and 12 had only coarse calcifications. The presence of punctate echogenic foci on sonography was 74% sensitive, was 46% to 53% specific, and had a positive predictive value of only 45% to 48% for the presence of psammomatous calcifications. The computed 2-tailed P value indicated that the punctate echogenic foci-to-psammoma body correlation was not statistically significant. The sonographic signature commonly referred to as "microcalcifications" may represent a variety of entities, including psammomatous calcifications, dystrophic calcifications, and eosinophilic colloid; for this reason, "punctate echogenic foci" would be a more accurate term.