Ovarian leiomyoma of uncertain primary versus secondary origin in a postmenopausal woman with uterovaginal prolapse: a case report and literature review

Ovarian leiomyomas are rare benign smooth-muscle tumors whose primary versus secondary origin may be difficult to establish. Distinction requires correlation of operative anatomy and histology and, when available, immunohistochemistry and molecular comparison with any uterine lesion. A 64-year-old para-6 postmenopausal Nigerian woman presented with a 2-year history of uterovaginal prolapse. Preoperative ultrasonography showed a fundal uterine leiomyoma measuring 5 × 6 cm but did not identify an adnexal mass. She underwent vaginal hysterectomy, anterior colporrhaphy, and left salpingo-oophorectomy after an unexpected firm left ovarian lesion was encountered. Gross pathology measured the uterine leiomyoma at 8.0 × 7.5 × 5.0 cm and the left ovary at 5.0 × 3.0 × 2.0 cm. Both uterine and ovarian lesions showed bland intersecting fascicles of smooth-muscle cells with eosinophilic cytoplasm, elongated blunt-ended nuclei, rare mitoses (< 1/10 high-power fields), and no significant atypia, tumor-cell necrosis, or vascular invasion. Histological similarity and a coexisting uterine leiomyoma raised the possibility of secondary involvement; however, no direct continuity, implantation, vascular spread, or molecular clonality was demonstrated. Immunohistochemistry was not performed because it was unavailable locally. The morphologic interpretation was consistent with ovarian leiomyoma of uncertain primary versus secondary origin. Recovery was uncomplicated, and the patient was well at the documented 6-week review. Ovarian leiomyoma should be considered in the differential diagnosis of a solid ovarian spindle-cell tumor, but morphology alone may not establish primary versus secondary origin. Careful assessment of the tumor–ovary interface and exclusion of leiomyosarcoma and sex cord-stromal tumors are essential; immunohistochemistry and molecular testing should be used when available.