Dermoid Cyst with Rokitansky Nodule
A dermoid cyst (mature cystic teratoma) with a Rokitansky nodule is a benign ovarian tumor characterized by a cystic mass containing fatty tissue, sebaceous material, hair, and other ectodermal derivatives, with the Rokitansky nodule representing a solid protuberance projecting into the cyst lumen that typically contains hair, teeth, cartilage, or bone 1, 2, 3.
Key Characteristics
Epidemiology and Clinical Features
- Most common ovarian tumor in younger women, accounting for 20% of all ovarian tumors and 69% of ovarian germ cell tumors 1, 3
- Occurs predominantly in reproductive-age women (median age 33-38 years) 4, 5
- 20% are asymptomatic and discovered incidentally 3
- Bilateral in approximately 10-15% of cases 4, 5
- Average size is 6-7 cm at diagnosis 4, 5
The Rokitansky Nodule (Dermoid Plug)
The Rokitansky nodule is the pathognomonic solid component that distinguishes dermoid cysts:
- Densely echogenic tubercle projecting into the cyst cavity 6, 5
- Contains complex tissue including hair, teeth, cartilage, and bone 2, 6, 7
- Present in approximately 92% of mature cystic teratomas 8
- Highly diagnostic when identified on imaging 3, 6
Imaging Characteristics
Ultrasound Features (First-Line Modality)
The diagnosis is typically made by ultrasound with characteristic appearances 1, 2:
Classic findings include 5:
- Unilocular cyst (58%) or multilocular cyst (15%) with mixed echogenicity
- "Dots and lines" pattern (hair floating in sebaceous material)
- Echogenic white ball appearance
- Acoustic shadowing (present in 72% of cases)
- Minimal or absent vascularity (Color Score 1-2 in 80%)
Novel ultrasound features identified 5:
- "Cotton wool tufts" appearance
- "Mushroom cap sign"
- "Completely hyperechogenic lesion"
- "Starry sky sign"
CT and MRI Characteristics
- Macroscopic fat with attenuation values less than -20 HU (mean -95 HU)
- Rokitansky nodule with calcifications (teeth, bone)
- Fat-fluid levels
- 96% diagnostic accuracy for mature cystic teratomas
- High signal intensity on T1-weighted images (sebaceous material)
- Chemical shift artifact at fat-fluid interface
- Fat-saturation sequences confirm fatty content
- 92% diagnostic accuracy with fat-suppression techniques
Clinical Management Considerations
Risk Stratification
According to O-RADS classification 10:
- Typical dermoid cysts <10 cm = O-RADS 2 (almost certainly benign, <1% malignancy risk)
- Dermoid cysts ≥10 cm = O-RADS 3 (low risk, 1-<10% malignancy risk)
Complications to Monitor
- Torsion occurs in 5.6% overall, with higher rates in larger cysts 4
- Malignant transformation is rare (1-2%), more common in postmenopausal women and advanced age 3, 4
- Chemical peritonitis from cyst rupture is extremely rare (1 in 394 spillage cases) 4
Surgical Approach
Fertility-sparing surgery is recommended for reproductive-age women 1:
- Minimally invasive surgery (laparoscopy) is preferred in >70% of cases 4
- Associated with decreased perioperative complications
- Higher cyst spillage rate but minimal clinical consequence
- Avoid radical surgery and full staging as unnecessary in benign disease 1
Important Clinical Pitfalls
⚠️ Do not confuse with immature teratoma: Immature teratomas have large irregular solid components with coarse calcifications and require chemotherapy 1, 7
⚠️ Fat content is not always pathognomonic: Some dermoids have high-density fat mixed with hair (density -13 to +8 HU), making diagnosis challenging 8
⚠️ Consider malignant transformation if: Patient is postmenopausal, cyst has irregular solid vascularized tissue without typical dermoid features, or rapid growth is documented 1, 3
⚠️ Bilateral disease: Always examine the contralateral ovary as 10-15% are bilateral 4, 5