A taller-than-wide shape in thyroid nodules in transverse and longitudinal ultrasonographic planes and the prediction of malignancy

Background: A "taller-than-wide" shape is associated with thyroid malignancy, but taller-than-wide in which plane is most accurate is unclear. We determined in which ultrasonography (US) plane a taller-than-wide shape is most predictive of malignancy. Methods: A total of 471 thyroid nodules from 435 patients were studied. The final diagnosis was based on histopathology in 145 nodules in 120 patients, and cytology in the remaining patients. A taller-than-wide shape was defined as a ratio of ≥1, calculated by dividing the anteroposterior diameter by the transverse diameter. Three criteria were formulated as follows: criterion 1, a taller-than-wide in any plane as a suspicious feature; criterion 2, that in the transverse plane; criterion 3, that in the longitudinal plane. The sensitivity, specificity, positive predictive value, negative predictive value, and area under the receiver operating characteristic curve (Az) were compared among the three criteria. Result: Of the 471 lesions, 125 (26.5%) were classified as malignant, and 346 (73.5%) were classified as benign. Criterion 1 showed high sensitivity (68%) and negative predictive value (87.7%), whereas criteria 2 and 3 showed high specificity (83.5% and 94.5%, respectively). The Az vale of criterion 1 was significantly higher than criteria 2 and 3 (p values = 0.0061 and 0.0362, respectively). Conclusions: A taller-than-wide shape was a useful US feature for predicting thyroid malignancy. Criterion 1, a taller-than-wide shape in either transverse or longitudinal plane, was most accurate and sensitive for predicting thyroid malignancy among the three criteria.