Thyroid calcification and its association with thyroid carcinoma

Calcification within the thyroid gland may occur in both benign and malignant thyroid disease, and its detection on ultrasonography is frequently dismissed by many clinicians as an incidental finding of little significance. As a tertiary referral center, most of our thyroid patients will have had thyroid ultrasonography before being referred to us, and in our experience, the incidence of malignancy in a thyroid nodule containing calcification seems to be higher than that in the average thyroid nodule. To assess this risk, we conducted this retrospective review.

Our analysis included 462 consecutive patients who underwent thyroid surgery at our institution between 1995 and 1999. We reviewed all the patients' charts for data regarding clinical findings, preoperative diagnostic investigations, and histopathologic diagnosis. Of the 462 patients, 361 (78.1%) had thyroid ultrasonography before surgery, and 49 (13.6%) of these ultrasounds showed intrathyroidal calcification.

Of the 49 patients whose ultrasounds showed intrathyroidal calcification, 29 (59.2%) were found on histopathologic examination to have thyroid carcinoma. Twelve of the remaining 20 patients had multinodular goiters. Of the 29 patients with malignancy, seven (24.1%) had preoperative fine-needle aspirates that were reported as benign. After excluding patients who were initially seen with multinodular disease, in the subset of 37 patients who presented with a solitary thyroid lesion with calcification, 28 (75.7%) were found to have carcinoma.

When calcification is noted within a solitary thyroid nodule, the risk of malignancy is very high. Surgery should be recommended regardless of the result of fine-needle aspiration cytologic findings.