Clinicopathological review of 46 primary retroperitoneal tumors.

Objectives: To clarify the clinical factors including diagnostic imaging findings that may correlate with the histopathological malignancy in primary retroperitoneal tumors.

Methods: The clinical backgrounds and imaging findings of 22 benign and 24 malignant primary retroperitoneal tumors were retrospectively investigated, and the prognosis of patients with malignant retroperitoneal tumors was assessed.

Results: There were significant correlations between the presence of symptoms and malignancy (P < 0.01), as well as between the irregularity of tumor margins and malignancy (P < 0.01). On dynamic magnetic resonance imaging (MRI), 90% of malignant tumors showed early enhancement either with quick or slow washout, while 75% of benign tumors showed delayed and no enhancement (P < 0.002). All malignant and benign paraganglioma showed the same early enhancement with quick washout. Malignant lymphoma showed various enhancement patterns. The 2-year and 5-year cause-specific survival rates of the patients with malignant retroperitoneal tumors were 68.0% and 43.2%, respectively. All malignant lymphoma patients were mainly treated with chemotherapy after being diagnosed histologically. Malignant paraganglioma patients who could not meet complete resection needed chemotherapy for promising survival.

Conclusion: The symptoms, the irregularity of the margins, and the specific enhancement pattern on the dynamic MRI may be important predictive factors of the primary malignant retroperitoneal tumors. Histological diagnosis was needed for malignant definition of paraganglioma because both benign and malignant paraganglioma showed similar clinical and imaging findings. Preoperative biopsy should be considered for selection of the appropriate treatment particularly in patients that are likely to have malignant lymphoma that could not be diagnosed definitively by the clinical and imaging findings.