Mary Catherine Frates MD, Presenter: Nothing to Disclose

Carol Beer Benson MD, Abstract Co-Author: Nothing to Disclose

Peter Michael Doubilet MD, PhD, Abstract Co-Author: Nothing to Disclose

Ellen Marqusee MD, Abstract Co-Author: Nothing to Disclose

Maricela Contreras MD, Abstract Co-Author: Nothing to Disclose

Edmund Cibas MD, Abstract Co-Author: Nothing to Disclose

Erik Alexander MD, Abstract Co-Author: Nothing to Disclose

P Reed Larsen MD, Abstract Co-Author: Nothing to Disclose

et al, Abstract Co-Author: Nothing to Disclose

To determine the likelihood that a thyroid nodule is malignant based on sonographic assessment of its size and cystic vs. solid composition.

From a prospectively collected database, we identified all thyroid nodules with maximum diameter of at least 10 mm that had ultrasound-guided thyroid biopsies between June 1995 and September 2000. For each nodule, we recorded two sonographic characteristics: maximum diameter and fraction of nodule that was cystic (subjectively assessed). Final pathologic diagnosis of each nodule, assigned based on surgical pathology when available and on cytology otherwise, was classified as benign, malignant, or unknown.

A total of 1217 nodules were included in our study, of which 178 had an unknown pathologic diagnosis and were excluded from the analysis. Of the 1039 nodules with known pathology, 108 (10.4%) were malignant. There was no significant relationship between nodule size and malignancy: the rate of malignancy was 9.0% in nodules with a maximum diameter of 10-14.9 mm (18 malignancies in 201 nodules), 9.4% in those measuring 15-19.9 mm (19/203), 9.5% in those 20-24.9 mm (19/200), 10.5% in those 25-29.9 mm (15/143), and 12.7% in those 30 mm or greater (37/292) (p=0.65, chi-square). There was a significant relationship between nodule composition and malignancy: the rate of malignancy was 12.5% in nodules that were <25% cystic (92 malignancies in 737 nodules), 6.3% in those 25-74% cystic (10/160), and 0.8% in those at least 75% cystic (1/119) (p<.0002, chi-square). (Composition was not available in 23 nodules.) Even among predominantly solid nodules (<25% cystic), the rate of malignancy was not associated with nodule size (p=0.64, chi-square).

In thyroid nodules at least 1 cm in maximum diameter, there is no relationship between nodule size and malignancy, but likelihood of malignancy is greater with mostly solid than mostly cystic nodules. The decision to biopsy a nodule should not be influenced by nodule size, but biopsy may be unnecessary in nodules at least 75% cystic.

Frates, M, Benson, C, Doubilet, P, Marqusee, E, Contreras, M, Cibas, E, Alexander, E, Larsen, P, et al, , Likelihood of Thyroid Cancer Based on Sonographic Assessment of Nodule Size and Composition.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4409626.html