Mature Cystic Teratoma
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Direct answer
A mature cystic teratoma, also called a dermoid cyst, is a benign germ cell tumour of the ovary made of tissue from all three germ layers, most often skin, hair and sebaceous material. It is the commonest ovarian germ cell tumour in women of reproductive age, and its main complications are torsion and rupture. Malignant change is uncommon and, when it occurs, is usually squamous cell carcinoma in older women.
What you must remember
- Origin: The tumour is derived from all three germ layers, so skin and adnexal structures, bone or cartilage and other mature tissues can coexist within one cyst.
- Typical contents: Sebaceous material, hair, and sometimes teeth or bone, which is why the cyst often looks complex on imaging.
- Ultrasound sign: An echogenic nodule projecting from the wall, called the Rokitansky nodule, often casting an acoustic shadow.
- CT or MRI: Macroscopic fat, shown as negative attenuation on CT, makes the diagnosis almost certain.
- Commonest complication: Adnexal torsion, so sudden severe pain in a patient with a known dermoid calls for urgent review.
- Bilateral disease: A minority of cases is bilateral, so the opposite ovary must always be inspected.
- Struma ovarii: A teratoma in which thyroid tissue predominates, which can cause thyrotoxicosis.
- Malignant change: Mostly squamous cell carcinoma in women usually older than 40 years, suspected from rapid growth or a large vascular solid area.
A stepwise route from imaging to ovary-sparing surgery
A woman in her late twenties presents with intermittent right lower abdominal pain and a 7 cm complex adnexal mass. The steps below show how the diagnosis is confirmed and the ovary conserved.
- Confirm on imaging: Transvaginal ultrasound usually shows an echogenic mass with a Rokitansky nodule. CT or MRI showing fat-density content settles the diagnosis when ultrasound is equivocal.
- Screen for torsion: Acute pain with nausea or vomiting means urgent laparoscopy, because torsion is the commonest complication and the ovary can often be saved if it is seen early.
- Choose ovary-sparing surgery: In a young woman, laparoscopic cystectomy removes the cyst wall while preserving normal ovarian tissue. Oophorectomy is reserved for a badly damaged ovary or suspected malignancy.
- Control spillage: Sebaceous contents cause chemical peritonitis, so the cyst is removed in a bag and the pelvis is irrigated after any rupture.
- Send for histology: Every specimen goes to pathology, and a frozen section is sent if a solid component looks atypical or the patient is older than 40.
Where the exam tries to catch you
Most traps come from treating a benign teratoma as either a cancer or a reason for radical surgery.
- Trap: Oophorectomy for every dermoid in a young woman Correct: Cystectomy with ovarian conservation is the default, since the lesion is benign and the ovary can usually be spared.
- Trap: Calling a Rokitansky nodule malignant on sight Correct: The nodule is a normal teratoma feature; suspicion of malignancy rests on age, rapid growth and a large vascular solid area.
- Trap: Ignoring thyroid function in a teratoma with thyroid tissue Correct: Struma ovarii can cause thyrotoxicosis, so thyroid function is checked when thyroid elements are seen.
Frequently asked questions
Which ultrasound feature is most typical of a mature cystic teratoma?
The Rokitansky nodule, an echogenic protrusion from the cyst wall, is the most typical ultrasound feature of a mature cystic teratoma. It often casts an acoustic shadow because of calcified or fatty contents. Its presence in a complex ovarian cyst should prompt a diagnosis of dermoid.
Why is the ovary conserved in torsion of a mature cystic teratoma?
A mature cystic teratoma is benign, and in young women preserving ovarian function matters. Detorsion with cystectomy keeps ovarian tissue even when the ovary looks dark, because it often recovers its blood supply after untwisting. Oophorectomy is reserved for a necrotic ovary that cannot be saved or for suspected malignancy.
What is struma ovarii and why does it matter in an exam?
Struma ovarii is a teratoma in which thyroid tissue makes up most of the mass. It can cause thyrotoxicosis, so thyroid function tests may be needed before surgery. Struma ovarii is managed surgically, with conservation of the ovary where possible in young women.
Which complication of a mature cystic teratoma is the most common?
Torsion of the adnexa is the most common complication of a mature cystic teratoma. The weight and mobility of the cyst make the ovary prone to twisting around its pedicle. Rupture with chemical peritonitis is the next important complication to recognise.
How is malignant change in a mature cystic teratoma usually recognised?
Malignant change is suspected when a dermoid grows quickly, when a solid component becomes large or vascular, or when the patient is older, usually beyond 40 years. Squamous cell carcinoma is the most common cancer arising in such a teratoma. Histopathology after surgery confirms the diagnosis.