Multifrequency magnetic resonance elastography (MRE) is a non-invasive method providing high-resolution stiffness maps of soft tissue based on differences in viscoelasticity. The aim of this prospective study was to establish multifrequency MRE for characterization of viscoelasticity of benign and malignant adrenal tumors.

15 healthy volunteers and 33 individuals with adrenal tumors were examined by multifrequency MRE. Patients with adrenal tumors underwent an adrenalectomy. Postoperatively, the results of pathological examination of adrenalectomy specimens showing 17 adrenal adenomas, 9 pheochromocytomas, 2 adrenocortical carcinomas, 3 metastases of other primary tumors, one sarcoma and one schwannoma were correlated with the preoperative findings of multifrequency MRE.

Multifrequency MRE was feasible in all subjects. Malignant tumors (adrenocortical carcinomas, adrenal metastases, and a sarcoma) showed higher stiffness than adenomas (p=0.01) and healthy adrenal glands (p<0.001). Adenomas were stiffer than healthy adrenal glands (p=0.005). Pheochromocytomas were also stiffer than adenomas (p=0.01) and healthy adrenal glands (p<0.001). In our cohort no difference in viscoelasticity could be shown between pheochromocytomas and malignant adrenal tumors (p=0.53). However, the diagnosis of pheochromocytoma was confirmed preoperatively in all cases based on elevated metanephrine and/or normatenapehrine levels in serum.

Multifrequency MRE enables a reliable determination of malignant adrenal tumors by detection of viscoelastic changes. It provides an excellent complement to traditional cross-sectional imaging and thus, serves as a biomarker enhancing preoperative interdisciplinary treatment decisions.