Primary versus secondary ovarian malignancy: Imaging findings of adnexal masses in the Radiology Diagnostic Oncology Group Study

PURPOSE: To analyze ultrasonographic (US), computed tomographic (CT), and magnetic resonance (MR) imaging features of primary and secondary ovarian malignant neoplasms to determine if there is any significant difference in their appearance. MATERIALS AND METHODS: Analysis of the multi-institutional Radiology Diagnostic Oncology Group data revealed 86 patients with primary ovarian carcinoma and 24 patients with a secondary ovarian neoplasm. Numerous imaging features that had been recorded for the adnexal masses with each imaging modality were reviewed and compared between primary and secondary malignant ovarian neoplasms. RESULTS: Of the imaging features assessed with all three modalities, multilocularity as determined at US (P =.02) or MR imaging (P =.01) was the only significant feature. At US, 30 (37%) of 81 primary ovarian cancers were multilocular, whereas only three (12%) of 24 metastatic neoplasms were multilocular. At MR imaging, 40 (74%) of 54 primary ovarian cancers were multilocular, whereas only five (36%)of 14 metastatic neoplasms were multilocular. Neither a predominately solid appearance nor bilaterality was significantly different between primary and secondary neoplasms. CONCLUSION: For malignant ovarian masses, multilocularity at MR imaging or US favors the diagnosis of primary ovarian malignancy rather than secondary neoplasm, but it is difficult to accurately distinguish between primary and secondary ovarian malignancies.