MR staging of endometrial cancer: Radiologic-pathologic correlation and cause of pitfalls

Learning objectives: to show the diagnostic performance and findings of Magnetic Resonance Imaging (MRI) in the staging of endometrial cancer and correlate them with histopathologic findings. To describe the possible causes of misdiagnosis in staging carcinoma of the endometrium. Background: the diagnosis of endometrial cancer is based on histological findings. Owing to its excellent soft-tissue contrast and free selection of imaging planes, MRI represents an important method in staging uterine neoplasms and provides useful information to address therapeutic strategy. Imaging findings: Endometrial cancer staging by MRI is based on the FIGO classification. T2-weighted images depict endometrial carcinomas as hyperintense masses with pathological endometrial thickening. A hyperintense disruption of the junctional zone is indicative of myometrial infiltration (stage-Ib). Deep myometrial involvement extending to the outer half of the myometrium characterizes stage-Ic. Causes of pitfalls includes atrophic uterus with insufficient delineation of the junctional zone, adenomyosis, leiomyomas. In stage-II the tumour invades the cervix. Cervical stromal invasion is suspected by recognizing the disruption of the cervical stroma of low intensity by the tumour; false-negative diagnosis can be result from associated small nabothian cysts. Stage-III is characterized by extension of the tumour beyond the uterus but not outside true pelvis. In stage-IV the tumour infiltrates bladder or rectal mucosa. Infiltration of the bladder or rectal wall is seen on T2-weighted images as a hyperintense disruption of the otherwise hypointense muscular layer. Conclusion: the radiologist should know the pathological-anatomical changes that occur in endometrial cancer and how they affect imaging in order to improve image interpretation and to avoid misdiagnosis.