Dermoid cyst, ovarian

Complications include torsion, rupture, infection and haemorrhage. Torsion occurs in up to 10% of dermoids, and is disproportionately common in dermoids when compared to other ovarian tumours. This may be because the tumour is often pedunculated. Perforation is rare, and may be acute, presenting as an acute abdomen, or chronic. In the latter case, slow leakage of sebaceous material from the cyst may cause a granulomatous peritonitis and result in a gross appearance resembling ovarian cancer, both on imaging and at surgery. Rupture may be triggered by pregnancy. Three very rare medical complications may develop; thyrotoxicosis (due to thyroid tissue), carcinoid syndrome (due to carcinoid tissue), or autoimmune haemolytic anaemia.

Malignant transformation is rare, occurring in 1-2% of cases. The risk is greater in postmenopausal women. The commonest tumour type to develop is squamous cell carcinoma, but malignant carcinoid tumours, undifferentiated carcinoma, adenocarcinoma, sarcoma, melanoma and basal cell carcinoma have all been reported.

Plain radiographs demonstrate suggestive pelvic calcifications, resembling teeth or bone, in 50% of cases (Fig.1), ultrasound (US) may show a solid cystic, or mixed solid and cystic adnexal mass (Fig.2). Sonographic features that suggest the specific diagnosis of dermoid cyst are the presence of hair, teeth, or Rokitansky protuberances (rounded polypoid soft tissue masses projecting into the lumen). However, US has limited sensitivity, and therefore imaging by CT (Fig.3) or MRI (Fig.4) may be preferred. Dermoid cysts are treated by resection with preservation of the adjacent ovarian tissue. The opposite ovary is inspected at surgery, and if normal, no further treatment is required. In peri - or post-menopausal patients, therapy usually consists of bilateral oophorectomy and hysterectomy.

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