Uterine müllerian adenosarcoma with sarcomatous overgrowth and lung metastasis in a 25-year-old woman.

Uterine müllerian adenosarcoma with sarcomatous overgrowth (MASO), uncommon in premenopausal women, is a rare variant of uterine adenosarcomas characterized by a sarcomatous portion constituting >25% of the tumor. Uterine MASO often appears as a benign, protruding cervical polyp. However, in contrast to typical müllerian adenosarcomas (MAs), MASO is a highly aggressive tumor, frequently associated with a fatal outcome. Though very rare in premenopausal women, because of the high aggressiveness and malignant potential, uterine MASO should be considered, even in women of a young age with benign-appearing polypoid masses, and treated aggressively at the time of initial diagnosis without delay. We present herein a case of uterine MASO in a 25-year-old woman with lung metastasis who was lost to follow-up for one month after the initial diagnosis had been established.