Fact-sheet: Dermoid of ovary - Mature cystic teratoma
Updated on 09/17/2021 at 12:16 PM
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Definition
Germ cell ovarian tumors: 20-25% of ovarian tumors (90-95%: teratomas)
Population: young women
Composed of at least 2 of the 3 germ cell layers
3 types of teratomas:
Mature cystic teratoma or dermoid cyst (90%)
Cyst (sebaceous or serous)
Rokitansky protuberance
Calcifications
Hair, fat, teeth
Immature teratoma (<1%)
Monodermal teratomas (goiters (3%), carcinoids and struma carcinoids)
Bilateral in 10% of cases
Arising from pluripotent germ cells, composed of tissues derived from the 3 embryonic layers:
- Ectoderm: nervous tissue, skin lining and pilosebaceous adnexa, teeth
- Mesoderm: fat, muscle, bone, cartilage
- Endoderm: intestinal or bronchial epithelium, thyroid tissue
The presence of fat within an ovarian tumor is considered nearly pathognomonic of a teratoma
-----> 93% of mature teratomas contain fat
In cases of cystic teratomas without sebaceous content (serous or mucinous), fat should be sought within the walls of the Rokitansky nodule
Fat is present in a teratoma in 2 forms:
-Sebum, produced by the pilosebaceous adnexa (ectoderm), filling the cyst cavity (liquid fat)
-Fatty tissue (mesoderm) visible in the cyst walls or in the Rokitansky nodule (adipocytes), sometimes associated with granulation tissue (lipophagic granuloma)
Mature cystic teratoma is most often fat-rich:
-Sebaceous content rich in fat
-Adipocytes within the Rokitansky nodule or wall
In cases of cystic teratomas without sebaceous content (serous- or mucinous-type fluid content), it is particularly important for diagnosis to look for fat within the cyst walls or within the Rokitansky nodule
The Rokitansky nodule represents the solid portion of the teratoma, composed of a mixture of mature tissues derived from the 3 embryonic layers
-Bone and teeth, when present, are located within the Rokitansky nodule
-Hair also arises from this nodule
After contrast injection, cyst enhancement is variable
Clinical features
Asymptomatic in most cases.
Occasionally, pelvic pain.
Discovered due to complications, notably cyst torsion.
A few reported cases of rupture with peritonitis
Ultrasound
First-line examination
To look for
Absence of septations
Fatty area, finely echogenic with posterior attenuation
Mixture of hair and sebum producing a horseshoe-shaped echogenic image with acoustic shadowing
Bone acoustic shadowing
Absence of Doppler signal within the Rokitansky nodule
CT
Fat is hypodense on CT, close to -100 HU
It is visible here in its 2 forms:
sebum,
and areas of fatty tissue within the Rokitansky nodule
MRI
3 methods allow confirmation of the presence of fat:
Selective fat saturation, causing a drop in fat signal
In-phase and opposed-phase gradient echo sequences (IP-OP), causing a drop in signal at fat/water interfaces
Chemical shift artifact along the frequency-encoding direction on spin echo sequences
Fat signal saturation is the most widely used technique
It allows in particular easy differentiation between a fatty lesion and a hemorrhagic lesion (endometrioma), both of which can appear as T1 hyperintense
