Comparative Study of Dynamic Susceptibility Contrast Perfusion MR Images between Warthin's Tumor and Malignant Parotid Tumors

Diagnostic imaging of salivary gland cancers: REFCOR recommendations by the formal consensus method

OBJECTIVE

To define the indications for each imaging modality in the screening, characterization, extension and follow-up of salivary gland tumors.

MATERIAL AND METHODS

The French Network of Rare Head and Neck Tumors (REFCOR) formed a steering group who drafted a narrative review of the literature published on Medline and proposed recommendations. The level of adherence to the recommendations was then assessed by a rating group, according to the formal consensus method.

RESULTS

If a swelling of a salivary gland is palpable for 3 weeks, an ultrasound scan is recommended to confirm a tumoral lesion and rule out differential diagnoses. For a salivary gland tumor, MRI is recommended with diffusion-weighted and dynamic contrast-enhanced techniques. In the case of histologically proven malignancy or a highly suspicious lesion, a CT scan of the neck and chest is recommended to assess the tumor, lymph nodes and metastases. FDG-PET is not currently recommended in routine clinical practice for initial diagnosis, assessment of extension, evaluation of response to treatment, staging of recurrence, or follow-up of salivary gland tumors.

CONCLUSION

Assessing salivary tumors is based on MRI. Extension assessment is based on neck and chest CT.

Advanced magnetic resonance imaging findings in salivary gland tumors

Salivary gland tumors (SGTs) make up a small portion (approximately 5%) of all head and neck tumors. Most of them are located in the parotid glands, while they are less frequently located in the submandibular glands, minor salivary glands or sublingual gland. The incidence of malignant or benign tumors (BTs) in the salivary glands varies according to the salivary gland from which they originate. While most of those detected in the parotid gland tend to be benign, the incidence of malignancy increases in other glands. The use of magnetic resonance imaging (MRI) in the diagnosis of SGTs is increasing every day. While conventional sequences provide sufficient data on the presence, localization, extent and number of the tumor, they are insufficient for tumor specification. With the widespread use of advanced techniques such as diffusion-weighted imaging, semi-quantitative and quantitative perfusion MRI, studies and data have been published on the differentiation of malignant or BTs and the specificity of their subtypes. With diffusion MRI, differentiation can be made by utilizing the cellularity and microstructural properties of tumors. For example, SGTs such as high cellular Warthin’s tumor (WT) or lymphoma on diffusion MRI have been reported to have significantly lower apparent diffusion values than other tumors. Contrast agent uptake and wash-out levels of tumors can be detected with semi-quantitative perfusion MRI. For example, it is reported that almost all of the pleomorphic adenomas show an increasing enhancement time intensity curve and do not wash-out. On quantitative perfusion MRI studies using perfusion parameters such as Ktrans, Kep, and Ve, it is reported that WTs can show higher Kep and lower Ve values than other tumors. In this study, the contribution of advanced MRI to the diagnosis and differential diagnosis of SGTs will be reviewed.