Microcalcification and Intranodular Coarse Calcification Are Often Found on Preoperative Ultrasounds of Papillary Thyroid Carcinoma
Stephanie L. Lee
Kim BK, Choi YS, Kwon HJ, Lee JS, Heo JJ, Han YJ, Park YH, Kim JH. Relationship between patterns of calcification in thyroid nodules and histopathologic findings. Endocrine J. October 6, 2012 [Epub ahead of print]. doi: 10.1507/endocrj.EJ12-0294.
SUMMARY • • • • • • • • • • • • • • • • • • • • • • • •
Thyroid nodules are commonly seen in adults. Studies suggest a prevalence of 2% to 6% on palpation, 19% to 35% on ultrasound, and 8% to 65% in autopsy data (1). Most professional endocrine professional societies’ guidelines, including the 2009 ATA guidelines (2), recommend sonographic examination as part of the evaluation for malignancy of all thyroid nodules. The sonographic features of microcalcification are highly specific (89.1% to 96.8%) but not sensitive (20% to 24.3%) for papillary thyroid carcinoma (3,4). Macrocalcification has previously been associated with an increased risk of thyroid malignancy (5). The objective of this study was to determine which pattern of calcification is predictive of malignancy in a large number of thyroid nodules confirmed as benign or malignant after resection.
Methods and Results
The aim of this study was to determine which pattern of calcification is associated with thyroid malignancy. This is a single-institution retrospective study of 1431 thyroid nodules in 1078 patients between January 2008 and July 2011 who had a preoperative ultrasound prior to thyroid surgery. The male:female ratio was 5.3:1 and the mean (±SD) age was 47.2±11.1 years. The reason for surgery was usually increased risk of malignancy or cosmetic concerns. Thyroid ultrasound was performed by two radiologists with a 5- to 12-MHz linear array transducer. All images were independently reviewed by an endocrinologist whose specialty was thyroid disease. The calcifications were categorized as microcalcification (fine stippling, 2 mm with acoustic shadowing within a nodule, or a calcified spot (single spot of macrocalcification not associated with a discrete nodule). The average size of the resected nodule was 1.2±0.8 cm (range, 0.1 to 6 cm). A total of 91.1% of the resected nodules were thyroid cancer and 8.9% were benign nodules; 94.7% of the malignancies were papillary thyroid carcinoma. The data were analyzed as a frequency with a 2-by-2 table to calculate sensitivity, specificity, and positive predictive value. Calcifications were detected in 38.6% of all nodules, 40.2% of malignant nodules, and 22.2% of benign nodules. The distribution of calcification in malignant nodules was microcalcification in 42.9%, intranodular in 26.5%, calcified spot in 13.4%, crescent in 11.1%, and annular-type in 5.9%. The only forms of calcification associated with thyroid malignancy were microcalcification (odds ratio [OR], 3.5; 95% CI, 1.6 to 7.7; P<0.001) and intranodular coarse calcification (OR, 2.4; 95% CI, 1.1 to 5.6; P = 0.035).
In this retrospective study, thyroid malignancy frequently was found on preoperative ultrasound to contain microcalcification (42.9%) and intranodular coarse calcification.
ANALYSIS AND COMMENTARY • • • • • •
Sonographic evidence of calcification is found in both benign and malignant nodules. This retrospective study is significant because of the large number of patients who had both a preoperative thyroid ultrasound and thyroidectomy to confirm pathology. A limitation of this study is that more than 90% of the subjects had thyroid cancer. The benign nodule cohort contained only 126 nodules, as compared with the cancer cohort, which contained 1305 nodules. Thus, the frequency of the calcification patterns cannot provide accurate statistics of sensitivity or specificity for detecting thyroid malignancy based on a preoperative ultrasound. This study does confirm that both microcalcification and intranodular coarse calcification are commonly seen in thyroid malignancy. It is important to recognize that other forms of calcification (annular, crescent, spot) can be seen in thyroid cancer and are not a sonographic sign that a thyroid nodule is benign
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CLINICAL THYROIDOLOGY • DECEMBER 2012 VOLUME 24 • ISSUE 12 • © 2012