Useful MRI findings for differential diagnosis of sublingual mass lesions

The purpose of this study is to identify useful MRI findings for differentiating sublingual mass lesions. MR images of 29 patients with sublingual swelling were retrospectively reviewed. Patients were categorized into 4 groups according to their final diagnoses: cysts, benign tumors, inflammation and malignant tumors. Clinical symptoms and MRI findings of the patients in each diagnostic category were investigated. Of 29 patients, 6 had benign tumors, 6 had ranula, 6 had inflammation, 11 had malignant tumors. Eighteen patients (62%) were correctly diagnosed as one of 4 disease categories by clinical findings alone. Signal intensity of lesions compared to the muscle and the normal sublingual space (SLS) was not characteristic for any of the diagnostic categories. Only ranulas showed homogenous signal intensity within the lesion on T2 images. Hemangiomas were easily diagnosed by the characteristic contour and architecture including flow void. All lesions with ragged boundaries were either inflammatory or malignant masses. The lesions with ragged boundaries accompanied by expansion of the SLS were inflammatory masses. The lesions with smooth boundaries and a capsule-like rim were either cysts or benign tumors. Utilizing these MRI findings, 25 of 29 patients (86%) were correctly categorized into one of 4 diagnostic categories. Four lesions without a capsule-like rim confined within SLS could not be correctly categorized. These were 2 cases of inflammatory mass and 2 cases of malignant salivary gland tumor. MRI findings were efficient for differentiation of sublingual mass lesions. However, some cases of malignant salivary gland tumor originating from the sublingual gland could not be differentiated on MRI findings from cases of chronic inflammation. (author)