Supplementary Material for: A case report: Ovarian fibrothecoma with minor sex cord elements

Introduction: Ovarian stromal tumors with minor sex cord elements are rare, and there are not specific imaging features to help in making the diagnosis. Case presentation: We report a case of this tumor in an 81-year-old woman who was referred to our hospital for constipation and a pelvic mass. Magnetic resonance imaging (MRI) demonstrated a well-circumscribed mass and isointensity compared to the skeletal muscle on T1-weighted imaging (T1WI) and low signal intensity mixed with high signal ranges on T2-weighted imaging (T2WI). Dynamic gadolinium-enhanced fat-suppressed T1WI revealed mild and increased enhancement of the peripheral area in the early and delayed phases, respectively. On diffusion-weighted imaging (DWI), a heterogeneously high signal intensity corresponding to the peripheral enhanced area was observed, and the apparent diffusion coefficient values of the high-intensity areas on DWI were low. Malignancy could be suspected, so the mass was surgically removed. Pathological assessment revealed a fibrothecoma with minor sex cord elements. Conclusion: The tumor’s preoperative diagnosis is difficult, although the possibility of this rare tumor from atypical findings on DWI and/or dynamic contrast enhancement studies should be considered.