Relationship of Shape of Macrocalcification and Thyroid Cancer: Correlation with US and Pathologic Findings

Lee, Sun Young; Lee, Han Bee; Cho, Woo Ho; Kim, Jae Hyung; Jeong, Myeong Ja; Kim, Soung Hee; Kim, Ji Young; Kim, Soo Hyun; Kang, Mi Jin; Lee, Jihae

Abstract

PURPOSE
The purpose of this study was to categorize macrocalcifications into several subtypes by the US findings and to determine which type of macrocalcification in a thyroid nodule is associated with thyroid malignancy.
MATERIALS AND METHODS
We retrospectively analyzed the macrocalcification patterns of thyroid nodules in 396 patients that underwent ultrasonography (US)-guided thyroid FNA or surgery in our institution between August 2009 and August 2011. Two radiologists evaluated US findings and categorized macrocalcifications into 5 subtyes : (A) solitary macrocalcification no association with thyroid nodule; (B) nodular macrocalcification(s) within indeterminate thyroid nodule; (C) dense macrocalcification without ability to interpret internal content by its posterior acoustic shadowing; (D) irregular-shaped macrocalcification(s); (E) macrocalcification with other suspicious malignant US finding(s). A chi-squared test and a Fisher exact test were used for comparison of categoric variables. The diagnostic sensitivity, specificity, positive and negative predictive values (PPV and NPV) were obtained.
RESULTS
Among total of 417 nodules, 114 (27.3%) were suspicious malignancy or malignancy on histopathological result. Macrocalcification with other malignant US feature had the highest incidence of malignancy (77.5%), followed by irregular-shaped macrocalcification(s) (43.9%), and dense macrocalcification without ability to interpret internal content by its posterior acoustic shadowing (38.5%), solitary macrocalcification no association with thyroid nodule (8.3%) respectively, and nodular macrocalcification(s) with indeterminate thyroid nodule had the lowest incidence (7.5%). A nodule with macrocalcification with other malignant US finding(s) has the highest odds ratio (42.52), followed by a nodule with irregular-shaped macrocalcification(s) (9.65) and dense macrocalcification (7.72). Leaving macrocalcification with compositive malignant findings aside, irregular-shaped macrocalcification is more likely to be associated with increased risk for malignancy compared with other patterns of macrocalcification.
CONCLUSIONS
Irregular-shaped macrocalcification is a fine indicator for differentiation between benign and malignant thyroid nodules on ultrasonography.