Imaging findings of ovarian dysgerminoma with emphasis on multiplicity and vascular architecture: pathogenic implications

We report the imaging findings of three ovarian dysgerminomas that coexisted with other germ cell tumors or gonadoblastomas, focusing on the distribution of tumor nests and vascular architecture, which might provide information about the pathogenesis of dysgerminomas. In a 14-year-old female with dysgerminoma and coexisting gonadoblastomas, contrast-enhanced magnetic resonance imaging (MRI) demonstrated a solid mass in the right ovary, which presented as hyperintense lobules on diffusion-weighted imaging separated by fibrovascular septa. Some small nodules were found to exist separately from the lobules (multiplicity) and to include pathological remnants of gonadoblastoma. Large tumor vessels were present at the center of the mass (central blood vessels), which were in direct contact with the ovarian veins and radiated peripherally through the fibrovascular septa. In a 35-year-old female, a mixed germ cell tumor, which was mainly composed of dysgerminoma and yolk sac tumor foci, exhibited the same vascular architecture pattern as the first dysgerminoma on contrast-enhanced computed tomography. In a 10-year-old female with a mixed germ cell tumor, contrast-enhanced MRI revealed an enlarged left ovary, which contained a large heterogeneous mass and multiple tiny nodules (multiplicity). Microscopically, the former corresponded to a yolk sac tumor, and the latter corresponded to a dysgerminoma containing remnants of gonadoblastoma. Based on these cases, the presence of tumor nest multiplicity and central blood vessels might aid the diagnosis of dysgerminoma, and these imaging findings might be indicative of the synchronous development of multiple dysgerminomas from primordial germ cells or gonadoblastomas.