Unexpected tumor-to-tumor metastasis of synovial sarcoma within leiomyoma: A case report and literature review.

A tumor metastasis within another tumor is known as tumor-to-tumor metastasis (TTM). We report a 43-year-old woman who presented with hypermenorrhea and an abdominal mass. She had history of a soft tissue tumor on her left ankle at 38 years of age. Laboratory data showed slight elevation of CA125 and no other abnormal findings and magnetic resonance imaging revealed a circumscribed margin mass in the uterine fundus. We diagnosed the mass as benign leiomyoma and performed total laparoscopic hysterectomy. Postoperative pathological examination revealed TTM of synovial sarcoma within the uterine leiomyoma. A database search identified 29 cases of TTM within uterine leiomyoma. The donor tumor was mostly breast cancer (in 23 cases). To the best of our knowledge, this is the first report of a sarcoma TTM to a uterine leiomyoma. Despite the difficulty of preoperative diagnosis, TTM should be considered during the treatment approach for a patient with leiomyoma and a history of malignant tumors.