MR imaging criteria for the prediction of extranodal spread of metastatic cancer in the neck.

BACKGROUND AND PURPOSE The presence of extranodal spread in metastatic nodes significantly affects treatment planning and prognosis of the patient with head and neck cancer. We attempted to evaluate the predictive capability of MR imaging for the extranodal spread in the neck. MATERIALS AND METHODS We retrospectively studied MR images from 109 patients with histologically proved metastatic nodes, of which 39 were positive for extranodal spread. We assessed 47 extranodal spread-positive and 130 extranodal spread-negative metastatic nodes by using the following MR imaging findings as the possible criteria for extranodal spread: 1) nodal size (short-axis diameter); 2) obliterated fat spaces between the metastatic node and adjacent tissues, such as the muscles and skin on T1-weighted images ("vanishing border" sign); 3) the presence of high-intensity signals in the interstitial tissues around and extending from a metastatic node on fat-suppressed T2-weighted images ("flare" sign); and 4) an irregular nodal margin on gadolinium-enhanced T1-weighted images ("shaggy margin"). Multivariate logistic regression analysis was conducted to identify independent predictive criteria for extranodal spread. RESULTS Nodal size, shaggy margin, and flare sign criteria were independent and significant MR imaging findings suggestive of extranodal spread in the metastatic nodes. We obtained 77% sensitivity and 93% specificity with the flare sign, 65% sensitivity and 99% specificity with the shaggy margin, and 80% sensitivity and 85% specificity with the size criterion (cutoff point = 16 mm). CONCLUSION Fat-suppressed T2-weighted and gadolinium-enhanced T1-weighted images are useful for the detection of extranodal spread in metastatic nodes in the neck.