The algorithm for imaging the salivary glands depends on the clinical scenario with which the patient presents to the clinician. Because of the importance of identifying small calculi in the gland or salivary duct as the cause of the symptom complex, nonenhanced computed tomography is often the best initial study for the evaluation of the painful gland. If an infiltrative neoplasm is highly suspected, nonenhanced and enhanced magnetic resonance (MR) imaging may be superior in demonstrating perineural, meningeal, and skull base invasion. Sialography is reserved for the evaluation of chronic sialadenitides unrelated to sialolithiasis. Thin-section MR techniques for MR sialography may soon replace conventional sialography.

Major salivary gland imaging.

PURPOSE: To evaluate the diagnostic value of gadolinium-enhanced dynamic magnetic resonance (MR) imaging of salivary gland tumors and correlate the MR imaging and histopathologic findings. MATERIALS AND METHODS: Thirty-three salivary gland tumors in 29 patients were examined preoperatively at gadolinium-enhanced dynamic MR imaging. There were 22 benign and 11 malignant tumors. Dynamic contrast material–enhanced MR images were obtained for 5 minutes. Time of peak enhancement (Tpeak) and washout ratio (WR) were determined from time–signal intensity curves (TICs). Microvessel count and cellularity-stromal grade were evaluated histopathologically. The strengths of correlations between Tpeak and microvessel count and between WR and cellularity-stromal grade were statistically analyzed to determine whether any differences among the various histopathologic tumor types existed. In a validation study, 13 salivary gland tumors in 13 patients were examined consecutively. RESULTS: At a Tpeak of 120 seconds, malignant...

Salivary gland tumors: Diagnostic value of Gadolinium-enhanced dynamic MR imaging with histopathologic correlation

Purpose: To determine the value of adding diffusion-weighted (DW) magnetic resonance (MR) imaging to dynamic contrast material–enhanced MR imaging when distinguishing between benign and malignant parotid tumors. Materials and Methods: This retrospective study was approved by the institutional review board, and the informed consent requirement was waived. The authors analyzed MR images of 50 lesions (36 benign, 14 malignant) in 47 patients. DW MR imaging and dynamic contrast-enhanced MR imaging were performed in all patients. Time-intensity curve (TIC) patterns were categorized as follows: type A, time to peak was more than 120 seconds; type B, time to peak was 120 seconds or less with high washout ratio (≥30%); type C, time to peak was 120 seconds or less with low washout ratio (<30%); and type D, flat. The apparent diffusion coefficient (ADC) values were measured on DW MR images. Sensitivity, specificity, accuracy, and positive and negative predictive values were calculated for type A, B, and D tumors re...

Parotid Gland Tumors: Can Addition of Diffusion-weighted MR Imaging to Dynamic Contrast-enhanced MR Imaging Improve Diagnostic Accuracy in Characterization?

BACKGROUND AND PURPOSE: Preoperative prediction of tumor malignancy is clinically very important, because this information strongly influences the surgical plan. We evaluate the preoperative apparent diffusion coefficient (ADC) maps of benign and malignant salivary gland tumors. MATERIALS AND METHODS: High-resolution MR imaging was performed on 31 patients with benign or malignant salivary gland tumors; ADC maps of the tumors were also obtained. Surface coils of 47 or 110 mm diameter were used to improve the image resolution. The ADCs were compared with histologic features of the excised tumors. RESULTS: The ADC maps effectively depicted the histologic features of the salivary gland tumors, such as presence of cancer cells, myxomatous tissues, fibrosis, necrosis, cyst formation, and lymphoid tissues. The ADC maps showed that more frequent areas with high ADCs (≥1.8 × 10−3 mm2/s) were significantly greater in benign tumors than in malignant tumors. The sensitivity and specificity for high ADC occupying fewer than 5% of the area of a tumor was 89% and 100%, respectively, resulting in 97% accuracy, 100% positive predictive value, and 96% negative predictive value. CONCLUSION: The ADC may provide preoperative tissue characterization of the salivary gland tumors.

http://www.ajnr.org/content/ajnr/28/1/116.full.pdf

Apparent diffusion coefficient mapping of salivary gland tumors: prediction of the benignancy and malignancy.

BACKGROUND AND PURPOSE: The surgical approach to parotid tumors is different for benign and malignant neoplasms, but the clinical symptoms do not correlate well with histology. Difficulties in tumor classification also arise in imaging modalities, in which sonography has the lowest and MR imaging, the highest accuracy. The purpose of this study was to review our experience using conventional MR imaging of the neck in the evaluation of parotid tumors and to evaluate which MR imaging findings are best able to predict malignant histology. MATERIALS AND METHODS: Eighty-four consecutive patients (43 males, 41 females; median age, 56 years; range, 9–85 years) with parotid gland tumors who underwent MR imaging before surgery were prospectively included in the present study and retrospectively analyzed. Histology was available for all tumors. We analyzed the following MR imaging parameters: signal intensity, contrast enhancement, lesion margins (well-defined versus ill-defined), lesion location (deep/superficial lobe), growth pattern (focal, multifocal, or diffuse), and extension into neighboring structures, perineural spread, and lymphadenopathy. RESULTS: The 57 (68%) benign and 27 (32%) malignant tumors consisted of 29 pleomorphic adenomas, 17 Warthin tumors, 11 various benign tumors, 5 mucoepidermoid carcinomas, 3 adenoid cystic carcinomas, 1 acinic cell carcinoma, 1 carcinoma ex pleomorphic adenoma, 9 metastases, and 8 various malignant neoplasms. Specific signs predictive of malignancy were the following: T2 hypointensity of the parotid tumor ( P = .048), ill-defined margins ( P = .001), diffuse growth ( P = .012), infiltration of subcutaneous tissue ( P = .0034), and lymphadenopathy ( P = .012). CONCLUSIONS: Low signal intensity on T2-weighted images and postcontrast ill-defined margins of a parotid tumor are highly suggestive of malignancy.

http://www.ajnr.org/content/ajnr/32/7/1202.full.pdf

MR imaging of parotid tumors: typical lesion characteristics in MR imaging improve discrimination between benign and malignant disease

Magnetic resonance (MR) imaging was performed in 116 patients in whom a parotid mass lesion was clinically suspected. Eighty-six patients had benign disease. The 30 patients in whom a malignant tumor was found were further evaluated. To determine which features are characteristic of malignant parotid tumors, spin-echo T1- and T2-weighted images of malignant lesions in the parotid gland were compared with those of benign disease. In our series, tumor margins, homogeneity, or signal intensity were not discriminative factors to correctly predict benign or malignant disease. Infiltration into deep structures (eg, the parapharyngeal space, muscles, and bone) was observed only in malignant tumors. Infiltration into subcutaneous fat was noticed in malignant as well as in inflammatory disease. No statistically significant correlation was found between tumor grade and MR imaging features in malignant disease. MR imaging is useful in delineating malignant tumors but is unreliable in correctly predicting the histologic nature of a mass lesion in the parotid gland.

N. J. Freling

Papers

Malignant parotid tumors - clinical use of mr imaging and histologic correlation