Dermoid cyst in pregnancy

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"dermoid cyst" AND pregnancy AND ovarian

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dermoid cyst ovary ultrasound pregnancy

A gray-scale transabdominal ultrasound image of the pelvic region demonstrating a large adnexal mass within the left ovary. The mass is characterized as a complex cyst with a well-defined, smooth wall. The internal architecture exhibits mixed echogenicity, featuring a predominantly hypoechoic central area with irregular, hyperechoic speckled internal contents and mural components. These features are suggestive of heterogeneous tissue types, such as sebaceous material or fat, commonly seen in a mature cystic teratoma (dermoid cyst). The image serves as a clinical example of pelvic sonography used to evaluate ovarian masses during pregnancy, highlighting the differentiation between simple and complex cystic structures based on internal echotexture and morphology.

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PMID: 36410423

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Dermoid Cyst (Mature Cystic Teratoma) in Pregnancy

What Is a Dermoid Cyst?

A dermoid cyst is the common name for a mature cystic teratoma, a benign germ cell tumor. It is the most common ovarian neoplasm encountered during pregnancy.

Gross pathology - the opened cyst shows hair, sebaceous material, teeth, and other tissue derivatives from multiple germ layers:

Opened mature cystic teratoma (dermoid cyst) showing hair and mixed tissue contents

Fig. Opened mature cystic teratoma (dermoid cyst) of the ovary - Robbins Pathologic Basis of Disease

Pathology

Cell of origin: Germ cells (ovum after first meiotic division); karyotype is almost always 46,XX
Gross: Unilocular cyst lined by gray-white wrinkled skin; contains hair shafts, sebaceous/oily material, teeth, and areas of calcification
Microscopy: Cyst wall of stratified squamous epithelium with underlying sebaceous glands, hair follicles, and adnexal structures. Tissues from all 3 germ layers present - cartilage, bone, thyroid, neural tissue
Bilaterality: 10-15% are bilateral
Malignant transformation: Occurs in ~1% - most commonly to squamous cell carcinoma; rarely thyroid carcinoma or melanoma
Germ cell tumors constitute 15-20% of all ovarian tumors; the majority are mature cystic teratomas in females of reproductive age

(Robbins, Cotran & Kumar Pathologic Basis of Disease)

Incidence in Pregnancy

Adnexal masses are identified in pregnant patients at a rate of 2-20 per 1,000 pregnancies - approximately 2-20x more frequently than in age-matched non-pregnant women. Among adnexal masses in pregnancy that require surgical management:

Type	Frequency
Dermoid cysts (MCT)	32% - most common
Endometriomas	15%
Functional cysts	12%
Serous cystadenomas	11%
Mucinous cystadenomas	8%

About 2% of adnexal masses in pregnancy are malignant, and approximately 70% of all adnexal masses spontaneously resolve during pregnancy.

(Cathcart et al., Am J Obstet Gynecol 2023 - PMID 36410423)

Ultrasound Appearance

Ultrasound is the mainstay of evaluation - safe, accurate, and widely available. Dermoid cysts appear as complex adnexal masses with:

Mixed echogenicity (hyperechoic foci from fat/calcification, hypoechoic areas)
A "tip of the iceberg" sign from dense hyperechoic material with posterior acoustic shadowing
Hyperechoic lines and dots ("dot-dash" pattern) from hair in sebaceous fluid
A Rokitansky nodule (dermoid plug) may be visible

Transabdominal ultrasound showing a complex left adnexal mass with mixed echogenicity consistent with a mature cystic teratoma (dermoid cyst)

Validated scoring systems (IOTA Simple Rules, ADNEX model, Lerner, Sassone) can help risk-stratify masses in pregnancy. MRI without gadolinium is preferred when ultrasound is inconclusive and further characterization is needed.

Clinical Presentation

Most dermoid cysts in pregnancy are asymptomatic and found incidentally on first-trimester ultrasound. When symptoms occur, they are usually due to a complication:

Torsion - most common complication; presents with acute pelvic/lower abdominal pain, nausea, vomiting. Risk is highest in early second trimester as the uterus rises and displaces the mass
Rupture - chemical peritonitis from spillage of sebaceous contents; causes severe abdominal pain, peritoneal signs
Obstruction of labor - if cyst is in the pouch of Douglas or lower pelvis, it can obstruct fetal descent
Infection - rare

Management

Expectant (Observation)

Recommended for:

Cysts <6 cm with benign ultrasound features
Asymptomatic masses with no concern for malignancy
Serial ultrasound monitoring throughout pregnancy

Surgical Intervention

Indicated for:

Cysts >6 cm (high torsion risk)
Symptoms of torsion, rupture, or acute abdomen
Masses with features concerning for malignancy
Masses expected to obstruct labor

Preferred approach: Laparoscopic surgery - consistently demonstrates shorter hospital stay, less postoperative pain, and evidence of lower fetal loss, preterm birth, and low birthweight compared to laparotomy.

Optimal timing: Second trimester (14-20 weeks) - balances time for spontaneous resolution, reduced risk of miscarriage vs. first trimester, and better visualization before the uterus becomes very large. However, necessary surgery should never be delayed solely due to gestational age.

Intraoperative Best Practices (Laparoscopy in Pregnancy)

Parameter	Recommendation
Positioning	Left lateral decubitus after first trimester
CO₂ insufflation	<12-15 mmHg
Monitoring	Intraoperative maternal capnography
Fetal monitoring	Pre- and post-operative FHR and contraction monitoring
Port placement	Adjusted for uterine size and mass location
Thromboprophylaxis	Both mechanical and chemical

At Term / During Labor

If discovered to obstruct labor: Cesarean section is preferred
Cystectomy may be performed at the time of cesarean delivery if feasible

Paraneoplastic Complications (Rare but Important)

Dermoid cysts can occasionally trigger anti-NMDAR encephalitis (inflammatory limbic encephalitis), which may present as psychiatric symptoms, seizures, or movement disorders. This may remit following removal of the tumor - especially important to consider in pregnant women with unexplained neuropsychiatric symptoms.

Ovarian dermoid cysts are also associated with warm autoimmune hemolytic anemia (AIHA) in rare cases.

Key Summary Points

Feature	Details
Most common ovarian tumor in pregnancy	Yes - 32% of surgically managed adnexal masses
Incidental discovery	Most common presentation
Most feared acute complication	Torsion
Most dangerous complication	Rupture (chemical peritonitis)
Investigation of choice	Ultrasound (MRI if needed)
Observation threshold	<6 cm, asymptomatic, benign features
Surgery threshold	>6 cm, symptomatic, suspicious features
Best surgical timing	Second trimester (14-20 weeks)
Preferred surgical route	Laparoscopy
Malignant transformation risk	~1%

Sources:

Robbins, Cotran & Kumar Pathologic Basis of Disease (mature cystic teratoma pathology)
Berek & Novak's Gynecology (germ cell tumors, ovarian mass evaluation)
Cathcart AM et al. Adnexal masses during pregnancy: diagnosis, treatment, and prognosis. Am J Obstet Gynecol 2023 (PMID 36410423) - most comprehensive recent review

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