Clinical and ultrasound features of ovarian sclerosing stromal tumors: a large single-center case series.

Background: Ovarian sclerosing stromal tumor (OSST) is a rare, benign sex cord-stromal tumor, often occurring in young women and presenting with nonspecific symptoms or hormonal effects. Its diagnosis remains challenging due to the limited systematic description of sonographic features in the literature, which frequently leads to preoperative misclassification as a malignant ovarian tumor and may result in unnecessary radical surgery. This study describes the clinical and sonographic characteristics of OSST in a large single-center cohort to improve its preoperative recognition. Methods: We conducted a retrospective review of patients with a pathological diagnosis of OSST at our institution between January 2008 and October 2025. Clinical data, ultrasound images, and pathological reports were systematically collected. All sonograms were reviewed by experienced sonographers to assess tumor morphology, internal architecture, and vascularity. Results: A total of 39 OSSTs were diagnosed. The majority of patients (79.5%) were symptomatic, most commonly presenting with menstrual disorders or abnormal vaginal bleeding (56.4%). The patients' ages ranged from 4 to 73 years. All tumors were unilateral. Sonographically, all lesions were well-defined, round or ovoid masses, predominantly with heterogeneous echotexture. Morphology varied: 18 were purely solid, 19 were solid-cystic, and 2 were completely cystic. Most exhibited moderate vascularity (color score 3, 31/39), with a characteristic pattern of regular peripheral vascularity observed in 25 cases (64.1%). In one case, contrast-enhanced ultrasound (CEUS) exhibited early hyperenhancement with a centripetal filling pattern, followed by a peripheral ring sign in the late phase. According to the Ovarian-Adnexal Reporting and Data System (O-RADS) classification, 36 tumors (92.3%) were categorized as intermediate to high risk (category 4 or 5), whereas the remaining three were assessed as category 2 or 3. Preoperative ultrasound suggested a specific benign diagnosis in only 4 cases (10.3%), whereas the majority (35/39, 89.7%) were classified as indeterminate. Fertility-sparing lesion excision was performed in 36 patients (32 lesion enucleations, 4 unilateral adnexectomies), and three postmenopausal patients underwent hysterectomy with bilateral adnexectomy. No recurrence was observed during follow-up. Conclusions: OSST presents across a wide age spectrum with nonspecific symptoms. Its sonographic features, particularly the combination of a well-defined solid-cystic mass with prominent peripheral vascularity, are characteristic but often lead to indeterminate or suspicious O-RADS classification. Awareness of its benign nature and variable presentation is crucial to guide appropriate, fertility-sparing surgical management.