A Case of Intramural Adenosarcoma With Sarcomatous Overgrowth Associated With Adenomyosis and Endometriosis.

Adenosarcoma is a mixed epithelial and mesenchymal neoplasm composed of a malignant mesenchymal component and a benign Müllerian glandular component. Although the endometrium is the most common primary site, adenosarcoma can also occur in the cervix, ovaries, fallopian tubes, vagina, or other sites outside the genital tract. This report presents the case of a 59-year-old woman with intramural adenosarcoma, associated with adenomyosis and endometriosis. Initially, a 4.0-cm uterine mass was identified via magnetic resonance imaging (MRI), and a watchful waiting approach was adopted. However, the mass grew to 8.5 cm over three months. A pathological examination revealed a polypoid mass with malignant spindle cells and benign glandular epithelium, confirming adenosarcoma with sarcomatous overgrowth. The endometrium showed no abnormalities, and the tumor appeared contiguous with adenomyosis and endometriosis in the myometrium and serosa of the uterine corpus, respectively. This case highlights the importance of considering adenosarcoma in the differential diagnosis of malignant transformation from adenomyosis or endometriosis.