Malignant Mixed Müllerian Tumor

Malignant mixed müllerian tumors (MMMTs), make up about half of all uterine sarcomas, but can originate anywhere along the lower female genital tract. Also known as carcinosarcomas, MMMTs contain both epithelial and stromal elements, unlike other uterine sarcomas, which contain only stromal elements. Advanced age, excess estrogen exposure, nulliparity, prior pelvic irradiation, and tamoxifen have been implicated as risk factors.

The uterus is most commonly involved organ. Ultrasound findings include expansion of the endometrial cavity with an intrauterine mass. The mass is usually hyperechoic to normal myometrium; however, homogeneous echogenic thickening of the endometrium can be the only finding.

CT will also depict expansion of the endometrial cavity (see images above) with an internal mass. The mass can be ill-defined or well-defined, but is usually heterogeneous and lower in attenuation compared to the normal myometrium. Areas of higher attenuation and calcifications can also be seen.

On MRI, MMMTs are heterogeneously hyperintense on T2-weighted images and slightly hypointense on T1-weighted images. Scattered areas T1-hyperintensity may be present, and there is heterogeneous and avid enhancement.

It is important to assess for myometrial involvement, metastatic pelvic and retroperitoneal lymphadenopathy, carcinomatosis, and adnexal involvement.

References

Teo SY, Babagbemi KT, Peters HE, Mortele KJ. Primary malignant mixed mullerian tumor of the uterus: findings on sonography, CT, and gadolinium-enhanced MRI. AJR Am J Roentgenol. 2008 Jul;191(1):278-83.