Leiomyomas are common benign gynecological tumors and usually arise in the uterus. The retroperitoneal cellular leiomyoma, one of the unusual manifestations, is a rare tumor. Diagnosis and treatment are challenges. We report a case of 65-year-old women presented with an asymptomatic mass beneath the right posterior vaginal mucosa. CT imaging revealed heterogeneous mass 6 cm in the pelvic cavity abutted lower segment of uterus, cervix, and vagina. The provisional diagnosis was subserosal cervical leiomyoma. She underwent exploratory laparotomy. Intra-operative, a normal size uterus was found separately from retroperitoneal pelvic mass at the level of internal os. Histological report confirmed cellular leiomyoma later. Total hysterectomy, bilateral salpingoophorectomy and completely excision of tumor were achieved with good outcome. Our patient represents the rare case of retroperitoneal cellular leiomyoma, which is hardly identified from internal examination and preoperative imaging. Surgical removal is essential for pathological diagnosis and treatment.

Keywords: Leiomyoma, Retroperitoneum, Cellular leiomyoma, Vaginal mass