"Cotyledonoid dissecting leiomyoma" or "Sternberg tumor" is a very rare variant of smooth muscle tumors with a distinctive gross appearance. We describe a similar lesion, probably the sixth reported case, comparing its clinicopathological features with those of previous cases. A 26-yr-old nulliparous woman underwent laparotomy for a large pelvic mass replacing the postero-lateral aspect of the uterus with extension into the left pelvic cavity in the form of numerous exophytic congested small nodules. The tumor was removed by resection without hysterectomy after frozen section examination. Histologically, there were variable sized micronodules of benign smooth muscle fascicles, which were separated by fibrous connective tissue with a marked hydropic change and rich vascularity. Immunohistochemical and ultrastructural studies were helpful for confirmation of the smooth muscle nature, but not useful for the definitive diagnosis. Due to bizarre, sarcoma-like gross appearances, this type of lesion should be subjected to frozen section examination in order to avoid overtreatment and preserve the fertility in young women.