Relationship between ultrasonographic and pathologic calcification patterns in papillary thyroid cancer

Ultrasonographic microcalcification is highly related to papillary thyroid cancer (PTC) and pathologic psammoma body is a poor prognostic factor. However, it is little known about whether the microcalcifications seen on ultrasonography are consistent with the pathologic psammoma bodies. We evaluated the relationship between ultrasonographic (US) calcification types and pathologic calcification features, and the consistency between observed pathologic and US calcifications. US calcifications were classified into microcalcification (MC) and nonmicrocalcification (non-MC) types, and pathologic calcifications were classified into 3 types: psammoma bodies, stromal calcifications, and ossifications. Among the 411 nodules that were reviewed by a pathologist, 38.9% (n = 160) had any type of US calcification. The larger the size of pathologic calcification, the more calcification was present in US (psammoma 46.1% < stromal 53.7% < ossification 73.3%). Psammoma bodies occurred in all US MC type. Ossification nodules occurred in nearly all (92.3%) non-MC type. The stromal-only nodules were 36.8% MC-type and 63.2% non-MC type. MC-type had a significantly higher odds ratio than non-MC type for predicting psammoma bodies according to the logistic regression. The presence of MC in ultrasonography was consistent with the presence of psammoma bodies. This study suggests that US identification of MC may be a useful prognostic indicator of PTC aggressiveness.