Case of the Week #566

Anna Meshkova; Alina Goryainova
Yaroslavl, Russia

Posting Dates: Aug 31, 2022 - Sep 14, 2022

Reviewer: Javier Cortejoso

Case Report: A 23-year-old G1P0 with no remarkable medical history was scanned at our unit at 18 weeks of gestation. Ultrasound examination at the first screening and at 17 weeks were reported to be normal.

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Answer

We present a case of intracranial teratoma.

Ultrasound imaging revealed the lesion approximately 26mm x 17mm x 23 mm located in the middle of the brain. The solid hyperechoic component measured 15mm x 16 mm. It was well defined, rounded, echogenic and heterogeneous with spots of hyperechogenicity. Color Doppler examination showed the presence of vascularization in the lesion. The other cerebral structures had a normal appearance, but some of them were compressed and displaced by the lesion. There was no extracranial abnormality.

The lesion was suspected to be a cerebral tumor due to its solid features and the presence of vascularization. Differential diagnoses were cerebral hemorrhage. Because of the early appearance of the lesion and its significant size, the prognosis was considered to be poor. A termination of pregnancy was discussed with the parents and was carried out at 19 weeks of gestation. Postmortem examination confirmed the diagnosis of intracranial teratoma, containing lung, bone, cartilage and neuroectoderm, with destruction of the central and right cerebral structures. Also the structures of the posterior fossa were displayed toward the cisterna magna.

Discussion

Congenital intracranial tumors are a rare occurrence, accounting for only 0.5–1.5% of all childhood brain tumors [1]. The most common of these tumors are teratomas, which comprise between 29% and 50% of central nervous system tumors. In childhood, teratomas have two peaks in their age distribution: 10% occur before 5 years of age whereas 48% occur between 5 and 14 years of age. Some consider that the incidence of teratoma in the first peak may be related to the sequestration of blastocyst cells before differentiation has occurred [2].

Teratomas are considered to be a subtype of germ cell tumors, containing all types of embryonic germ cell layers: ectoderm, mesoderm, and endoderm [3]. They are often immature because of primitive neural elements and, rarely, a component of mixed malignant germ cell tumors. Although they are tumors of the gonads, they can originate outside of the gonads. Extragonadal teratomas are congenital midline tumors, located both intracranially and extracranially, such as in the mediastinum and retroperitoneum. They are considered to originate from primordial germ cells that fail to migrate properly during the initial weeks of embryonic development [4].

Congenital intracranial teratomas are the most frequent intracranial tumor of the perinatal and neonatal period, comprising around 62% of prenatally detected cases [5]. They occur five times more frequently than astrocytoma, which is the second most common type of congenital intracranial tumor [6,7]. Teratomas occur almost exclusively above the tentorium. In a review by Wakai et al of 200 cases, only one was found in the posterior fossa [8].

Prenatal diagnosis of these tumors has increased in recent years. Diagnosis can be suspected on routine fetal ultrasound examination. It may show intrauterine ventriculomegaly, enlarged biparietal diameter, and/or brain tumor [9]. Intracranial teratomas are usually diagnosed by sonographic examination in the second or third trimester and early diagnoses are not as common [10-16]. If fetal ultrasound is suggestive of ventriculomegaly due to a tumor, MRI is advised for further localization, size estimation, and determination of the tumor extent, as well as ventriculomegaly [9,17]. Karyotyping is not recommended routinely but should be discussed if other abnormalities are present [18].

Subdural hemorrhage should be considered as a differential diagnosis in cases of intracranial space-occupying lesion [19]. Like teratomas, it is usually located in the supratentorial region. Predisposing factors may include maternal anticoagulant therapy, abdominal trauma, and fetal coagulation disorders, although may also occur spontaneously. In the present case, color Doppler imaging showed vascularization in the lesion which helped confirm the diagnosis of tumor.

Early diagnosis is important as termination of pregnancy may avoid obstetric complications. Ventriculomegaly may be responsible for macrocephaly and secondary dystocia by cephalopelvic disproportion. In this situation, Cesarean section is performed in about 60% of cases [5,9,17,20-21]. In addition to hydrocephalus, other common clinical conditions at the time of presentation are polyhydramnios, followed by respiratory distress and stillbirth [20].

The prognosis for intracranial teratomas is poor and the survival rate is less than 10% [5,14,22,23]. A large number of affected fetuses die prenatally and the rest shortly after birth [6]. Outcomes are dependent on the time of diagnosis and the size of the teratoma. In a review of 73 teratomas, the 1-year survival rate of infants with congenital intracranial teratoma was 7.2% [8]. Fukuoka et al describe an infant that survived until 3 years of age with adjuvant chemotherapy and complete surgical resection [24]. Partial resection does not appear to confer same benefits on long-term survival [25]. The location and the size of the teratoma are considered as significant prognostic factors rather than the histological grade [6], with the rarer posterior fossa teratomas being associated with worse outcomes.

References

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