A Case of Spontaneously Developed Retroperitoneal Parasitic Leiomyoma.

Spontaneous retroperitoneal parasitic leiomyomas are extremely rare and are mostly located in the pelvic cavity. Herein, we present a case of a small primary parasitic leiomyoma arising in the retroperitoneum. A 46-year-old Japanese woman presented with iron deficiency anemia. The patient had not undergone any abdominal surgeries. Transvaginal ultrasonography and MRI revealed multiple uterine myomas and an 18-mm, low-intensity mass adjacent to the uterus. The patient underwent a total laparoscopic hysterectomy. A solitary retroperitoneal tumor in the pouch of Douglas was resected. Histologic examination of the resected retroperitoneal tumor revealed a well-circumscribed benign leiomyoma. In this case, we suggest that retroperitoneal primary parasitic leiomyoma may have arisen independently of uterine leiomyoma. Further investigations of similar cases may fully elucidate the pathogenesis of primary retroperitoneal parasitic leiomyomas.