Carcinosarcomas of the uterus, previously known as malignant mixed Müllerian tumors (MMMT) of the uterus, are the most common (up to 50%) type of uterine sarcoma. They are thought to account for 2-8% of all malignant uterine cancers 1,2. The uterus is the most common site for carcinosarcomas of the female genital tract 1.
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Terminology
Carcinosarcomas of the female genital tract were previously known as malignant mixed Müllerian tumors to reflect the admixed histology comprising both epithelial and mesenchymal tissue. There is now increasing evidence to show that carcinosarcomas of the uterus are an aggressive subtype of endometrial carcinoma, where the tumor cells instead demonstrate epithelial-mesenchymal transition. Thus the 5th edition of the WHO classification of female genital tumors (2020) recommends that the term "malignant mixed Müllerian tumor" is no longer used 5.
Pathology
A uterine carcinosarcoma can be either homologous (contains uterine tissue types) or heterologous (contains tissues not usually present in the uterus e.g. rhabdomyosarcoma, chondrosarcoma or osteosarcoma elements) 5.
Similar to carcinosarcomas in general, they are composed or both carcinomatous (epithelial) and sarcomatous (mesodermal) components. Usually, the epithelial component dominates 2.
Prevalent subtypes for the epithelioid component include:
- endometrioid adenocarcinoma: most common epithelioid subtype 2
- clear cell carcinoma
- serous carcinoma
Prevalent subtypes for the sarcomatoid component include:
- undifferentiated sarcoma: homologous tumors
- rhabdomyosarcoma: heterologous tumors
Radiographic features
A uterine carcinosarcoma commonly presents as an intracavitary mass with coexistent dilatation of the endometrial canal.
Ultrasound
Often hyperechoic on ultrasound 1.
CT
Often heterogeneously hypodense and ill-defined on contrast-enhanced CT 1. Dilatation of the uterine cavity can be appreciated in the vast majority of cases.
MRI
They are not considered to have a pathognomonic appearance on MRI, with appearances often indistinguishable from those of endometrial adenocarcinoma.
However, reported general signal characteristics include 3.
- T1: predominantly isointense to both myometrium (~75%) and endometrium (~70%)
-
T2
- hyperintense to myometrium (~90%)
- either hypointense (~55%) or isointense (~41%) to the endometrium
-
T1 C+ dynamic
- <1 min: hypointense (~40%) or isointense (33%) to myometrium
- 1-4 min: hypointense (~60%) to myometrium
- >4 min: isointense (56%) to myometrium
Treatment and prognosis
Like other carcinosarcomas, they are highly aggressive tumors and carry a poor prognosis.
Differential diagnosis
General considerations include: