Cystic change in thyroid carcinoma: Prevalence and estimated volume in 360 carcinomas

The aim of this study was to determine the prevalence and amount of cystic change in thyroid cancer. This study also examined associated sonographic characteristics of cystic malignant thyroid nodules to help recognize these clinically important nodules.

This study was a retrospective review of 360 malignant thyroid nodules surgically removed at our institution between January 1, 2002 and December 31, 2004. All patients had signed research authorization. All patients had preoperative sonograms and surgical pathologic proof of their thyroid malignancy. The 360 malignant nodules were found in 307 patients. All scans were performed using 7- to 15-MHz transducers, and most studies included a digital video clip of the cancer. The preoperative ultrasound examinations were retrospectively reviewed by three radiologists and a sonographer. An estimate of cystic component percentage was derived by consensus. The presence of a mural nodule, thick irregular wall, microcalcifications, and prominent vascularity was also recorded.

Of the 360 carcinomas, 318 (88.3%) were solid to minimally (less than 5%) cystic, 33 (9.2%) were 6-50% cystic, 9 (2.5%) were 51-100% cystic. Of the nine (2.5%) malignancies that were greater than 50% cystic, all had other suspicious findings including mural nodules, microcalcifications, increased vascularity, and/or a thick irregular wall about the cystic portion.

The vast majority (88%) of thyroid cancer is uniformly solid or has minimal (1-5%) cystic change by sonography. Marked cystic change (>50% of the nodule) occurred in only 2.5% of cancers, which had other sonographic findings worrisome for malignancy.