Dermoid Ovarian Cyst

A dermoid cyst is a mature cystic teratoma of the ovary. It is the commonest ovarian neoplasm in women under 30, accounting for 10 to 20 percent of ovarian tumours and about 70 percent of benign tumours in this age group.

It is a germ cell tumour containing well differentiated tissues of ectodermal origin (skin, hair, sebaceous glands, teeth). It often also contains mesodermal and endodermal derivatives (fat, bone, cartilage, thyroid, neural tissue).

It is usually unilateral (about 10 to 15 percent bilateral), 5 to 10 cm in size, and slow growing. Most cases are asymptomatic and detected incidentally.

Complications are torsion (3 to 16 percent), rupture (1 to 4 percent), infection and malignant transformation (about 1 to 2 percent, mostly squamous cell carcinoma in postmenopausal women).

• Asymptomatic in most (about 60 percent), found at imaging, at caesarean section, or at routine examination.
• Pelvic pain or pressure, abdominal distension, urinary frequency, or constipation when large.
• Acute pain from torsion (sudden severe unilateral pain with nausea and vomiting, adnexal mass), most often in cysts 5 to 10 cm.
• Rupture: sudden pain and peritonitis; spillage of sebaceous material causes chemical peritonitis and later granulomatous reaction with adhesions.
• Associated autoimmune haemolytic anaemia, and anti-N-methyl-D-aspartate (NMDA) receptor encephalitis in young women with neural tissue in the teratoma (psychiatric symptoms, seizures, dyskinesias, dysautonomia and reduced consciousness).
• Struma ovarii (thyroid tissue) may cause hyperthyroidism in about 5 percent.

• Transvaginal ultrasound: a mass with a hyperechoic nodule (Rokitansky nodule or dermoid plug) with acoustic shadowing, "tip of the iceberg" sign, echogenic lines and dots (hair), fat fluid level, and calcification (teeth); characteristic appearance reaches diagnostic accuracy above 90 percent; no internal flow on Doppler.
• MRI with fat suppression shows signal loss in fatty components when the diagnosis is uncertain; CT shows fat, calcification and teeth.
• Tumour markers (CA-125, AFP, hCG, LDH, CEA, CA 19-9) when solid components or atypical features are present; squamous cell carcinoma antigen is raised in malignant transformation.
• Suspicious features: solid enhancing component, rapid growth, size above 10 cm in postmenopausal women, invasion or ascites.
• Thyroid function if features of thyrotoxicosis; and NMDA receptor antibody testing in cerebrospinal fluid and serum if neuropsychiatric symptoms.

• Surgical removal is the standard, because of the risks of torsion, rupture, infection and transformation, and because they rarely regress.
• Small asymptomatic cysts (below 5 cm) can be observed with ultrasound at 6 months, then yearly, as the rate of complication is low. Offer surgery when the cyst grows above 5 to 6 cm, becomes symptomatic, or has suspicious features.
• Laparoscopic ovarian cystectomy (preferred) is ovary sparing. Peel the cyst out from the ovarian cortex within an endobag to prevent spillage, and drain it by aspiration in the bag when large. Irrigate copiously with warm saline in case of spillage (to prevent chemical peritonitis).
• Cyst rupture does not worsen outcome but should be avoided. The ovary is closed by suturing or left to heal.
• Open surgery for very large or suspicious masses.
• Oophorectomy for postmenopausal women, women with completed childbearing, or with malignant suspicion; frozen section when malignancy is suspected.
• Torsion: urgent laparoscopic detorsion and cystectomy (or delayed cystectomy at 6 to 8 weeks), preserving the ovary even if it looks dusky.
• Bilateral cysts: bilateral cystectomy, with maximum ovarian tissue conservation.
• NMDA-receptor encephalitis: urgent tumour removal plus immunotherapy.
  • First line: methylprednisolone 1 g intravenously daily for 3 to 5 days, and intravenous immunoglobulin 0.4 g/kg daily for 5 days or plasma exchange.
  • Second line: rituximab 375 mg/m2 weekly for 4 doses, or cyclophosphamide.
• Malignant transformation: staging surgery and chemotherapy as for epithelial ovarian cancer or the relevant histology.
• Follow up: ultrasound at 6 months and then yearly for recurrence (about 4 percent) and for the contralateral ovary (4 to 10 percent develop a new dermoid).
• Pregnancy: asymptomatic cysts may be observed, with elective cystectomy in the second trimester if above 6 cm or symptomatic; torsion needs urgent surgery.