Our poster presents MR imaging characteristics of histologically-validated mature and immature teratomas of different age groups found at different common and rare anatomic locations.
- Teratomas identified during fetal life: intracranial, intraorbital, cervical, sacrococcygeal locations.
- Teratomas diagnosed in the pediatric and adult population: sacrococcygeal, pelvic and ovarian locations.
Before elaborating on the MRI characteristics of teratomas, we briefly describe the features observed in other imaging modalities.
Plain radiograph
It shows non-specific calcification, which may be suspicious for the presence of mature teratoma. A calcified capsule or ectopic tooth may be seen.
Ultrasound
It is a radiation-free modality, which can provide first-line diagnosis in case of pelvic or testicular localization, in particular.
Mature teratoma is typically seen as an inhomogeneous cystic mass, which contains some echogenic components within. Vascularity is usually not visible in the lesion. With ultrasound, sometimes we can see Rokitansky protuberances.Fig. 4
CT
CT has a high sensitivity in the diagnosis of mature teratomas.
Teratomas appear as lesions containing cystic and solid components. If you see the presence of fat attenuation within a cyst, calcified wall, and Rokitansky nodules on the images, it is highly suggestive of mature cystic teratoma. CT has higher sensitivity to identify calcifications and tooth components than MRI.Fig. 5
Its primary disadvantage is that it comes along with a relatively high amount of ionizing radiation.
MRI
The sensitivity of MRI in the diagnosis of mature teratoma -compared to CT- is similarly high, but unlike the latter, it is an ionizing-radiation free procedure.
On MRI -as well as in ultrasound and CT- the teratomas are usually heterogeneous, multiloculated cystic or solid lesions that may contain calcifications, ossifications, fatty components, or more complex tissues as hair or teeth.
Fat -one of the hallmarks of teratomas- is exquisitely examinable with MRI. With the help of MRI, fat can be distinguished from blood. On MR sebaceous fat within the tumor produces high signal intensity on T1-weighted images. On T2-weighted images, the signal intensity of the sebaceous component is various, frequently analogous to the fat tissue.
Unfortunately, blood components of some hemorrhagic lesions may have an equivalent combination of different signal intensities on T1- and T2- weighted images, but with the fat suppression techniques, as Dixon and CHESS, we can suppress the high signal of fat; therefore we can differentiate teratomas from these types of lesions. However, the use of the STIR sequence is not recommended because it may suppress the signal of hemorrhagic and sebaceous fat equally.
Gradient echo sequences are useful when the mature teratomas contain little fat within the cyst cavity or in the cyst wall, because of as echo time of fat and the water are in the opposite phase; therefore, we can detect the microscopic fat.
In immature forms, scattered fat and calcification with solid components are occasionally seen. Although solid parts are usually recognized as immature elements, mature teratomas may also have solid components, called Rokitansky protuberances.
To reduce fetal motion during an intrauterine examination of teratomas, the use of ultrafast MRI sequences, like HASTE and TRUFI, are suggested.
The following table shows a comparison between imaging modalities in the diagnosis of teratomas:
Fig. 6: Comparison between imaging modalities in diagnosis of teratomas
References: Imaging Diagnostic Center, BAZ County Central Hospital, Miskolc, Hungary
In the following, we will demonstrate MRI characteristics of teratomas with the help of the imaging records of our hospital.
Cases from fetal life
Case 1: Female fetus 33rd week of gestation. Left orbital lesion was recognized with 3D ultrasound 31st week of gestation.Fig. 7;Fig. 8
Diagnosis: Mature orbital teratoma
Learning point: On MRI, the teratomas appear as heterogeneous, multiloculated cystic, or solid lesions. They, especially in the head-neck region, do not respect the anatomical borders of each compartment, therefore sometimes it is hard to identify the exact origin of the lesion.
Case 2: Male fetus 31st week of gestation. Neck teratoma was identified with conventional ultrasound in scheduled examination.Fig. 9
Diagnosis: Immature neck teratoma
Learning point: The HASTE sequence can be acquired very rapidly; therefore, it will result in fewer motion artifacts. In contrast, the Trufi sequence takes a little bit longer, and with this technique, there will be more chemical shift artifacts. However, it has a better spatial resolution than the HASTE, especially in the visualization of the cardiovascular system[4;5].
Case 3: Male fetus 33rd week of gestation. Sacrococcygeal teratoma was recognized with conventional ultrasound in scheduled examination.Fig. 10;Fig. 11
Diagnosis: Mature sacrococcygeal teratoma
Learning point: Sacrococcygeal teratomas may be classified by location, according to Altman.
Altman’s type I: developing entirely outside the body
Altman’s type II: developing mostly outside the body, with intrapelvic presacral extension
Altman’s type III: developing mostly inside the body, with extension through the pelvis into the abdomen
Altman’s type IV: developing entirely inside the pelvis
Altman I or II type teratomas can cause severe complications during delivery; therefore, it is essential to determine the teratoma’s exact localization and extension.
Cases from pediatric and adult life
Case 4: 3-month-old female infant. She had a severe, multiple developmental disorder. Fig. 12
Diagnosis: Mature facial teratoma
Learning point: CT is more sensitive to identify the calcifications or ossifications than MRI, conversely in the case of the fat, the reverse is true. The fat suppression sequences, as Dixon or CHESS, provide excellent characterization about teratoma.
Case 5: 15-year-old female teenager. An abdominal ultrasound performed due to abdominal pain revealed a sizeable pelvic lesion.
Diagnosis: Mature ovarian teratoma
Learning point: Ovarian teratomas are mainly characterized by the presence of Rokitansky protuberances and fat-fluid level.Fig. 13;Fig. 14
Testis is one of the most common localisations of the teratoma. However, due to its anatomical localization, primarily only an ultrasound examination has been performed. Therefore the testicular teratoma case wasn't presented in this poster.