Fact-sheet: Dermoid of ovary - Mature cystic teratoma
Updated on 11/05/2026 at 12:21 PM
View all RADEOS cases associated with this fact-sheet
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
Laboratory findings
Aucun marqueur sérique spécifique.
Le CA 19-9 peut être élevé dans un tératome mature bénin. Une élévation isolée ne permet pas de conclure à une transformation maligne.
Radiography
Découverte fortuite de calcifications dentiformes ou de structures osseuses au sein d’une masse pelvienne, parfois associées à une clarté graisseuse.
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
Vascular intervention
Éviter la ponction-aspiration d’un dermoïde typique en raison du risque de dissémination intrapéritonéale de sébum et de péritonite chimique.
Classification
O-RADS US v2022 :
- Dermoïde typique < 10 cm : O-RADS US 2 (risque de malignité < 1 %).
- ≥ 10 cm : O-RADS US 3 si la morphologie reste typique.
- En présence d’un caractère atypique, reclasser selon la morphologie et la vascularisation. Une composante hyperéchogène avasculaire avec ombre acoustique est un signe classique du dermoïde.
O-RADS MRI 2024 :
- Lésion graisseuse typique, y compris avec un petit nodule de Rokitansky discrètement rehaussé, quelle que soit la taille = O-RADS MRI 2.
- Lésion graisseuse contenant un volume important de tissu rehaussé = O-RADS MRI 4.
- Implants péritonéaux tumoraux = O-RADS MRI 5.
Differential diagnosis
Endométriome : Hypersignal T1 persistant après saturation de la graisse, souvent associé à une diminution du signal T2 (shading).
Kyste hémorragique fonctionnel : Réseau fibrineux ou caillot rétractile avasculaire. L’hypersignal T1 hématique persiste après saturation de la graisse. La régression au contrôle conforte le diagnostic.
Teratome immature : Chez l’adolescente ou la femme jeune, volumineuse masse à prédominance solide, hétérogène et vascularisée, avec petits foyers graisseux et calcifications dispersées.
Transformation maligne d'un teratome mature : Surtout après la ménopause. Portion tissulaire irrégulière et rehaussée développée dans un dermoïde, particulièrement suspecte en cas de croissance ou de franchissement pariétal.
References
- RSNA. Outwater EK, Siegelman ES, Hunt JL. Ovarian Teratomas: Tumor Types and Imaging Characteristics. RadioGraphics, 2001. Voir également Adnexal Torsion: Review of Radiologic Appearances. RadioGraphics, 2021. RadioGraphics
- ESR et ESUR. Mature cystic teratoma of the ovary: a cutting edge overview on imaging features. Insights into Imaging, 2017. ESUR female pelvis group approach to cystic female pelvic lesions. Insights into Imaging, 2026. Springer Nature Link
- American College of Radiology. O-RADS US v2022 — Assessment Categories and Classic Benign Lesions. O-RADS MRI — Assessment Categories and Governing Concepts, 2024.
