Leiomyomas
Leiomyomas are the most frequent myometrial masses,
arising from uterine smooth muscle.
They are classified according to their situation in the myometrium as submucosal,
intramural and subserosal.
MRI is the most sensitive technique for detection and characterization of leiomyomas.
They typically appear as well-demarcated,
round and homogenous masses,
hypo intense on T2 weighted-images Fig. 1,
intermediate intensity signal on T1 Fig. 2,
without diffusion restriction Fig. 3 .
Decresead signal intensity on both diffusion sequences are called blackout phenomenon and is a suggestive criterion of benignity.
However,
various degenerative changes may occur in benign leiomyomas and influence their appearance.
Degeneration of leiomyomas result from blood supply disorder.
It has different types: hyaline,
myxoid,
cystic,
hemorrhagic and sarcomatous.
Hyalin leiomyoma is the most common degeneration form (60%).
it shows homogenous low signal intensity on T2 and has low enhancement.
Myxoid degeneration shows mucinous lakes on T2 Fig. 4 with increased ADC and progressive enhancement Fig. 5 .
Cystic leiomyomas appear as solid mass with internal fluid areas Fig. 6 without enhancement after contrast injection Fig. 7.
Myoma's bleeding occurs in gestation,
post-partum period and also during using oral contraceptives and shows peripheral rim hyper signal intensity on T1 and hypo signal intensity on T2 and does not enhance after contrast Fig. 8
Calcifications are frequently found (hypointense non-enhancing areas on all sequences).
Cellular myomas present high T2 signal intensity,
diffusion restriction (ADC usually more than 1) and greater enhancement Fig. 9.
Lipoleiomyomas are rare,
often found in postmenopausal period, induced by a macroscopic fat component,
(T1 and T2 hyper intensity with signal loss on fat saturated sequences) Fig. 10.
Currently,
there is no imaging argument for degeneration into or de novo lipoleiomyoma
Adenomyomas
Adenomyosis is defined as ectopic endometrial mucosa within the myometrium and surrounding smooth muscle hypertrophy. Focal form presents adenomyomas which can be submucosal,
intramyometrial and subserosal.
It appears as unwell surrounded mass with low T2 signal intensity containing internal high T2 signal intensity,
usually without mass effect on the endometrium.
They have relatively high ADC and are distinguishable from sarcomas Fig. 11.
Cystic adenomyoma corresponds to hemorrhage of an ectopic glandular.
In MRI,
the central fluid has high intensity signal T1 and T1FS,
its signal is variable on T2.
The T2 hyposignal wall appearance and haemorrhagic content is suggestive of cystic adenomyoma.
A liquid-liquid level may be seen.
Sarcomas
Myometrial sarcomas are heterogenous group including leiomyosarcoma and malignant mixed epithelial and mesenchymal tumors (MEMTs).
Leiomyosarcoma is the most frequent type arising from the myometrial smooth muscle. They are usually solitary intramural masses and may arise rarely from a myoma.
The most common MRI appearance is a large infiltrating myometrial mass with irregular,
poorly defined margins; heterogeneous T1 signal; hyper intensity signal on T2 with central necrosis,
restricted diffusion and early heterogeneous enhancement due to necrosis and hemorrhage Fig. 12.
The most suggestive signs of malignancy are: Ill-defined margins,
central necrosis and hemorrhage,
and rapid growth.
Combining three of these criteria have the highest sensitivity and specificity to differentiate leiomyosarcoma from atypical leiomyoma.
Recent studies fixed a cut-off ADC value of 1.1 to separate mass with high risk of malignity.
Lakhman et al evaluate in 2017 study a new imaging techniques textural analysis using semi-automatic method in purpose to differentiate leiomyosarcoma from atypical leiomyomas.
It consists of the measuring flatness or uniformity of the gray levels histogram from T2 weighted images.
MRI elastography is also under investigation and preliminary results for these two new techniques are encourageing.
Malignant mixed müllerian tumors (MMMTs) are mixed tumor composed by epithelial and mesenchymal component.
They present imaging features similar to those of endometrial carcinoma.
Carcinosarcoma commonly appears as well-defined masses with myometrium epicenter in 4% whereas it is endometrial in 88%.
Usually,
the tumor has high intensity on T2,
may present hyper intense area on T1 due to hemorrhage and has delayed heterogenous enhancement.
Endometrial stroma sarcoma arises from endometrial stroma.
ESS can mimic cystic leiomyoma Fig. 13 .
In these cases,
rapid growth,
irregular margin,
peripheral hypo intense rim on T2,
necrosis and hypo enhancement are the main criteria to suspect ESS.
Lymphoma
It is a rare condition with initial uterine involvement occurring in only 1% of patients with lymphoma.
Cervix involvement is more common than corpus.
Most of them are non-Hodgkin lymphomas.
Uterine lymphoma usually occurs as secondary involvement of the uterus with established extra uterine involvement.
It commonly appears as a diffuse enlargement with respect of the zonal architecture on T2 weighted images,
homogenous signal intensity,
and moderate uniform enhancement.
lymphoma may appear as a not sharply delineated myometrial homogeneous intermediate signal intensity mass on T1 and T2 weighted images.
Metastatic myometrial tumors
It has various imaging expressions as single or multiple nodules,
or diffuse myometrial infiltration.
Breast (especially invasive lobular carcinoma) and colon cancers are the most common primary neoplasms.
Diffusion is very useful in the detection of these involvements.
Uterine arteriovenous malformation (AVM)
Uterine AVMs are vascular abnormalities which may be congenital,
arising from vascular embryologic disorder,
or acquired usually following uterine trauma (curettage procedures,
caesarean section or pelvic surgery).
Infection,
gestational trophoblastic disease,
gynecological neoplasm and exposure to diethylstilbestrol are also associated conditions.
MRI is a problem-solving noninvasive tool in uterine AVMs.
It allows accurately to detect and to characterize these vascular disorders.
MRI findings include an enlarged uterus,
poor defined mass margin,
junctional zone interruption,
serpiginous flow voids in the myometrial wall and large parametrial vessels F Fig. 14 .
MR angiography shows abnormal vessels that enhance as intensely as normal ones and detect early venous return Fig. 15 .