VALUE OF THE CRITERION OF ASYMMETRY FOR T HE DIAGNOSIS OF SMALL PELVIC LYMPH-NODE IN MRI (INFERIOR OR EQUAL TO 1 CM)

The purpose of this study was to determine if lymph node asymmetry in small (<1.0 cm) pelvic nodes was a significant prognostic feature in d etermining metastatic disease. 216 patients who presented pelvic carci noma underwent MR Imaging. They were correlated to pathological findin gs obtained by surgery. We considered on the axial plan the maximum di ameter (MAD) of both round or oval-shaped suspicious masses. Two diffe rent cut-off values were determined : node diameter superior to 1.0 cm (criterion 1) and node diameter superior to 0.5 cm with asymmetry rel ative to the opposite side for nodes ranging from 0.5 cm to 1.0 cm (cr iterion 2). With criterion 1 MR Imaging had an accuracy of 88%, a sens itivity of 65%, a specificity of 96%, a PPV of 88% and a NPV of 88% in detection of pelvic node metastasis. By considering criterion 2, MR I maging had an accuracy of 85%, a sensitivity of 75%, a specificity of 89%, a PPV of 71% and a NPV of 91%. Normal small asymmetric lymph node s were present in 5.6% of cases. Asymmetry of normal or inflammatory p elvic nodes is not uncommon. It cannot be relied on to diagnose metast atic involvement in cases of small suspicious lymph nodes, especially because of its low specificity and positive predictive value.