MRI findings of mucoepidermoid carcinoma of the parotid gland: correlation with pathological features.

OBJECTIVE

The aim of this study was to correlate the MRI appearance and pathological findings in each grade of the mucoepidermoid carcinoma (MEC) of the parotid gland.

METHODS

We reviewed surgically proven MECs of parotid glands in 20 patients. Pathologically, 5 tumours were high-grade, 3 were intermediate and 12 were low-grade. MR images were evaluated with emphasis on signal intensities on T(2) weighted images, margin characteristics and lymph node metastasis, correlating these with pathological features.

RESULTS

Among the high-grade MECs, four out of five tumours showed inhomogeneous low to intermediate signal intensity on T(2) weighted images, reflecting high cellularity. All tumours had an ill-defined margin, reflecting invasive tumour growth. Among the intermediate-grade MECs, all three tumours showed intermediate signal intensity on T(2) weighted images and two tumours had an ill-defined margin. Among the low-grade MECs, 11 of the 12 tumours had a hyperintense area on T(2) weighted images because of the existence of abundant mucin secreting cells. Seven tumours had an ill-defined margin, reflecting peritumoural inflammatory changes rather than invasive tumour growth. Lymph node metastasis was seen in three high-grade MECs.

CONCLUSION

MECs of the parotid gland show variable MRI findings reflecting their histological nature, which seems to have certain tendencies depending on the tumour grade.