Mature Cystic Teratoma

Mature cystic teratoma is a benign ovarian germ cell tumour of well differentiated tissues from all three germ cell layers. It arises parthenogenetically from a single post-meiotic germ cell (46,XX homozygous). It makes up 10 to 25 percent of all ovarian tumours and about 60 percent of benign ovarian neoplasms, with peak incidence between 20 and 40 years.

Grossly, it is a unilocular cyst filled with sebaceous material and hair. A protuberance of solid tissue (the Rokitansky nodule or dermoid plug) contains skin, hair follicles, sweat and sebaceous glands, teeth, bone, cartilage, thyroid, respiratory and gastrointestinal epithelium, and neural tissue.

It is bilateral in 10 to 15 percent and multiple in 2 to 4 percent. Struma ovarii (over 50 percent thyroid tissue) and carcinoid tumours are specialised variants.

• Most are asymptomatic; incidental detection on imaging or at caesarean section.
• Torsion (3 to 16 percent; risk is higher with a size of 6 to 10 cm, pregnancy and the postpartum period): sudden unilateral severe pain, vomiting, and an adnexal mass.
• Rupture, spontaneous (1 to 4 percent) or at surgery: peritonitis from sebaceous contents causing chemical peritonitis, adhesions, and granulomatous peritoneal reaction (mimics carcinomatosis); delayed rupture can cause chronic inflammation.
• Infection (about 1 percent) and abscess formation.
• Malignant transformation (0.2 to 2 percent; squamous cell carcinoma in 80 percent; usually in women over 45 to 50 years, with tumour above 10 cm and a rapidly growing solid component): pelvic pain, mass, ascites.
• Hormonal: hyperthyroidism (struma ovarii in about 5 percent of cases with thyroid tissue); carcinoid syndrome (rare).
• Autoimmune: anti-NMDA receptor encephalitis in young women with neural tissue (usually under 35 years), with psychiatric symptoms (anxiety, psychosis), seizures, memory loss, dyskinesias (orofacial), autonomic instability, and hypoventilation; autoimmune haemolytic anaemia.

• Transvaginal ultrasound is accurate: hyperechoic mass with shadowing (dermoid plug), echogenic lines and dots (hair), "tip of the iceberg" sign, fluid fat level, and calcifications; no internal vascularity on colour Doppler.
• CT and MRI: fat attenuation or signal that suppresses on fat saturated sequences, calcification, and teeth; they also demonstrate complications.
• Features of malignant transformation: solid enhancing nodule projecting from the wall, invasion into adjacent structures, ascites, lymphadenopathy, rapid size increase; squamous cell carcinoma antigen and CA 19-9 may be raised. Torsion is suggested by an enlarged ovary with oedema and reduced Doppler flow, though normal flow does not exclude it.
• In suspected encephalitis: anti-NMDA receptor antibodies in cerebrospinal fluid (more sensitive than serum), MRI brain, electroencephalogram (extreme delta brush), and screening of the ovaries with imaging.
• Thyroid function tests when features of hyperthyroidism, with radioactive iodine uptake in the pelvis in struma ovarii.

• Surgery is advised for symptomatic cysts, cysts over 5 to 6 cm, growing cysts, suspicion of malignancy, torsion, and in postmenopausal women. Small asymptomatic cysts under 5 cm can be monitored with ultrasound at 6 months and then yearly.
• Laparoscopic ovarian cystectomy preserving ovarian tissue is the procedure of choice in reproductive age women.
• Strip the cyst from the ovarian cortex and remove it in an endoscopic bag, avoiding spillage. Remove any spilled material with copious warm saline irrigation (to prevent chemical peritonitis). Close the ovary with sutures or leave it open.
• Recurrence is about 3 to 4 percent, and 4 to 10 percent develop a contralateral teratoma, so inspect the other ovary.
• Oophorectomy for postmenopausal women, women with completed childbearing, large tumours with minimal residual ovarian tissue, or suspected malignancy.
• Torsion: immediate laparoscopic detorsion and cystectomy (or later cystectomy after oedema settles), conserving the ovary; the ovary frequently recovers even when blue or black.
• Pregnancy: observation of asymptomatic teratomas; elective laparoscopic cystectomy in the second trimester (14 to 20 weeks) for large (above 6 cm) or symptomatic cysts; emergency surgery for torsion or rupture.
• Anti-NMDA receptor encephalitis: urgent resection of the tumour (cystectomy or oophorectomy) with first line immunotherapy (methylprednisolone 1 g intravenous daily for 3 to 5 days, intravenous immunoglobulin 0.4 g/kg daily for 5 days, or plasma exchange).
• If there is no improvement in 2 to 4 weeks, give second line rituximab 375 mg/m2 weekly for 4 doses or cyclophosphamide 750 mg/m2 monthly.
• Recovery is slow (months), with relapses in 10 to 20 percent. Provide seizure control and intensive care when needed.
• Struma ovarii with hyperthyroidism: antithyroid drugs (carbimazole 15 to 40 mg daily or methimazole 10 to 30 mg daily) until euthyroid, then surgical removal; radioiodine ablation is used for malignant struma ovarii.
• Malignant transformation: staging laparotomy with hysterectomy, bilateral salpingo oophorectomy, omentectomy, and chemotherapy with carboplatin AUC 5 to 6 and paclitaxel 175 mg/m2 every 21 days for 6 cycles for stage IC and above; prognosis is poor in advanced stages (5-year survival 15 to 30 percent).
• Follow up with ultrasound at 6 and 12 months, then annually if conserved ovarian tissue.