MRI appearances of uterine malignant mixed müllerian tumors.
OBJECTIVE
Uterine malignant mixed müllerian tumors (MMMTs) are rare aggressive tumors with a high incidence of lymphatic, peritoneal, and pulmonary metastases. Preoperative differentiation from endometrial adenocarcinoma would be beneficial because their prognoses differ.


METHODS
We retrospectively reviewed MRI examinations of 51 histologically confirmed MMMTs. Tumor size, growth pattern, and imaging characteristics were recorded. Data were compared with MRI appearances of 73 endometrial adenocarcinomas.


RESULTS
On T1-weighted images, MMMTs were predominantly isointense to myometrium (76%) and endometrium (71%), with heterogeneous texture in 33% of cases and hyperintense foci in 27% of cases. On T2-weighted images, 92% of MMMTs were hyperintense to myometrium and either hypointense (55%) or isointense (41%) to endometrium. In 12% of cases, large heterogeneous MMMTs obliterated uterine architecture and were aggressive in appearance, whereas in 88% of cases, the appearances were indistinguishable from those of endometrial adenocarcinoma. Significantly more MMMTs than endometrial adenocarcinomas had cervical invasion (p = 0.008) and nodal enlargement (p = 0.00008). Dynamic contrast-enhanced images (available for 19 of 51 patients) obtained at less than 1 minute after administration of contrast agent showed MMMT enhancement to be hypointense (42%; 5/12 patients) or isointense (33%; 4/12 patients) to myometrium; between 1 and 4 minutes after administration of contrast agent, tumors were hypointense (58%; 7/12 patients); and at more than 4 minutes after administration of contrast agent (n = 18), MMMTs were isointense in 56% of cases. This finding is significantly different from that for endometrial adenocarcinoma, where enhancement is less than that of myometrium in 90% of cases (p = 4 × 10⁻⁸).


CONCLUSIONS
MMMTs do not have a pathognomonic MRI appearance. However, radiologic suspicion should increase in the presence of large heterogeneous infiltrative tumors or when tumoral enhancement equals or exceeds that of myometrium.
Bharwani
Nishat
N
Department of Cancer Imaging, St. Bartholomew's Hospital, Barts and The London NHS Trust, West Smithfield, United Kingdom.
Newland
Anwen
A
Tunariu
Nina
N
Babar
Syed
S
Sahdev
Anju
A
Rockall
Andrea G
AG
Reznek
Rodney H
RH
D000230:Adenocarcinoma / Q000473:pathology; D000368:Aged; D000369:Aged, 80 and over; D016009:Chi-Square Distribution; D003287:Contrast Media; D016889:Endometrial Neoplasms / Q000473:pathology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008536:Meglumine; D008875:Middle Aged; D018200:Mixed Tumor, Mullerian / Q000473:pathology*; D009942:Organometallic Compounds; D012189:Retrospective Studies; D014594:Uterine Neoplasms / Q000473:pathology*
D003287:Contrast Media; D009942:Organometallic Compounds; D008536:Meglumine; C072417:gadoterate meglumine