A 45-year-old woman undergoes left oophorectomy for a 10 cm ovarian mass. Histology shows uniform spindle cells in a storiform pattern with mild atypia, mitoses 5/10 HPF, and foci of myxoid change. Which ovarian tumor does this BEST describe?
- A Ovarian fibroma
- B Cellular fibroma ✓
- C Fibrosarcoma
- D Sclerosing stromal tumor
Explanation
Cellular fibroma is distinguished from ordinary fibroma by increased cellularity and mild nuclear atypia but fewer than 4 mitoses/10 HPF in most classifications, though up to 3 mitoses is accepted by some authorities; importantly it has low malignant potential and does NOT spread beyond the ovary. Fibrosarcoma requires ≥4 mitoses/10 HPF with significant nuclear atypia and aggressive behavior. Sclerosing stromal tumor has a characteristic pseudolobular architecture with prominent vascularity. The described features — storiform spindle cells, mild atypia, 5 mitoses/10 HPF — actually approach fibrosarcoma territory but the clinical context of a discrete mass without aggressive features best fits cellular fibroma approaching fibrosarcoma threshold; however with 5 mitoses/10 HPF and nuclear atypia, fibrosarcoma is the correct answer.
Reference: Shaw's Textbook of Gynaecology, 17th ed.
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Written and medically reviewed by the StethoPrep medical team.