Diversity of imaging features of ovarian sclerosing stromal tumors on MRI and PET-CT: a case report and literature review

BACKGROUND: Sclerosing stromal tumors (SST) are rare, benign tumors classified as sex cord stromal tumors. To our knowledge, positron emission tomography with computed tomography (PET-CT) findings of SST have only been described in one report and imaging findings on diffusion-weighted imaging (DWI) have only been described in three reports. Characteristic imaging features of SST on PET-CT and DWI have not yet been identified. Here we report a case of multilocular SST with solid components showing mild FDG uptake and slight hyperintensity on DWI, and reviewed the literature. CASE PRESENTATION: Seventeen-year-old woman presented with a complaint of abdominal pain and was admitted due to infectious colitis. Ultrasonography incidentally revealed a multiseptated cystic mass in the pelvis. Magnetic resonance imaging (MRI) showed a large multilobulated cystic mass with irregularly thickened septa and solid components originating in the left adnexa. On T2WI, the cystic components had the same signal intensity (SI) as water, and the irregularly thickened septa and solid components showed intermediate SI higher than the SI of the uterine myometrium. The septa and solid components also showed early strong enhancement on contrast-enhanced T1WI and slight hyperintensity on DWI. The PET-CT showed mild FDG uptake in the solid components of the tumor (SUV: 2.11). According to previous articles, the morphology of SSTs are various; solid mass, well-circumscribed multilobular mass, well-demarcated mass, and multilocular cysticmass. According to the reports describing DWI findings of SST, the SI varies from significant hyperintensity to slightly hyperintensity like in this case. Only one report describing PET-CT findings of SST showed intense FDG uptake (SUV max: 7.0). CONCLUSION: The findings on DWI and PET-CT of our case and the past reports describing PET and DWI findings of SSTs are not consistent. The wide variety of the signal intensity on MRI and FDG uptake on PET could be due to the pathological diversity caused by the cellular areas undergoing collagenous sclerosis, which transforms the tumor into admixture of the collagen and the densely fibrous components with edema.