Shape, margin, echogenicity and presence of calcification are helpful criteria for the discrimination of malignant from benign nodules; the diagnostic accuracy of ultrasonographic (US) criteria is dependent on tumor size, according to a retrospective review published the June issue of Radiology.
Won-Jin Moon, MD, from the department of radiology at Kangbuk Samsung Hospital, in Seoul, South Korea, and colleagues from the Thyroid Study Group of the Korean Society of Neuro- and Head and Neck Radiology, evaluated the diagnostic accuracy of US criteria for the depiction of benign and malignant thyroid nodules by using tissue diagnosis as the reference standard.
From January through June 2003, 8,024 consecutive patients had undergone thyroid US at nine affiliated hospitals, according to the researchers. A total of 831 patients (716 women; mean age, 49.5 years) with 849 nodules (360 malignant, 489 benign) that were diagnosed at surgery or biopsy were included in the study, the authors wrote.
They said that three radiologists retrospectively evaluated the following characteristics on US images: nodule size, presence of spongiform appearance, shape, margin, echotexture, echogenicity and presence of microcalcification, macrocalcification or rim calcification.
Moon and colleagues found statistically significant malignancy were a taller-than-wide shape (sensitivity, 40 percent; specificity, 91.4 percent); a spiculated margin (sensitivity, 48.3 percent; specificity, 91.8 percent); marked hypoechogenicity (sensitivity, 41.4 percent; specificity, 92.2 percent); microcalcification (sensitivity, 44.2 percent; specificity, 90.8 percent); and macrocalcification (sensitivity, 9.7 percent; specificity, 96.1 percent).
The US findings for benign nodules were isoechogenicity (sensitivity, 56.6 percent; specificity, 88.1 percent) and a spongiform appearance (sensitivity, 10.4 percent; specificity, 99.7 percent), according to the researchers.
The investigators found that the presence of at least one malignant US finding had a sensitivity of 83.3 percent, a specificity of 74 percent and a diagnostic accuracy of 78 percent. For thyroid nodules with a diameter of 1 cm or less, the sensitivity of microcalcifications was lower than that in larger nodules (36.6 vs. 51.4 percent), the authors wrote.