Retromolar trigone tumors: evaluation by magnetic resonance imaging and correlation with pathological data

The aim of this study was to evaluate the diagnostic accuracy of magnetic r esonance (MR) images to establish both the T stage and the relationships be tween the tumors and the surrounding structures in retromolar trigone tumor s. Twenty-two patients with squamous cell carcinoma of the retromolar trigo ne were examined by MR with a superconductive scanner operating at 1.5T. Th e study was performed with spin-echo (SE) T1 and T2 and short SE T1 sequenc es (TR 180 ms, TE 15 ms) after the administration of 0.2 mmol/kg of gadolin ium-DTPA (Gd-DTPA). The mandible was studied with SE T1weighted sequences a nd GE sequences. The results were compared with the pathological data on th e T stage (TNM classification) and the involvement of the surrounding struc tures. A positive correlation was Found in 19 of the 22 patients with an ac curacy of 86%. In one patient, the lesion was classified as T1 by MR which, at surgery, resulted being T4, given the infiltration of the cortical mand ible (this infiltration was too limited). In another, the MR showed a T4 le sion because of the presence of low signal intensity in the mandibular marr ow with enhancement after the Gd-DTPA injection without cortical erosion, w hile pathological data revealed a T2 lesion (this signal intensity was seco ndary to inflammation). In another case, the lesion was classified as T1 by MR which, at surgery, proved to be a T1 lesion. In assessing the involveme nt of the surrounding structures, MR showed a high accuracy, specificity an d sensitivity (> 90%). Five false positive cases were observed: in two beca use of infiltration of the masseter muscle and in the other three, because of infiltration to the pterigoid muscle, mandible and tonsillar bed, respec tively, due to the close contact between the tumors and the surrounding str uctures. Only one false negative case was observed with infiltration of the mandibular marrow. In evaluating the low signal intensity of the mandibula r marrow, the accuracy of MR was 87%, the specificity 77% and the sensitivi ty 100%. In one case, perineural spread along the mandibular nerve was foun d. In conclusion, MR proved to be highly accurate to study the T stage and examine the relationships between the surrounding structures in cases of re tromolar trigone tumors. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.