Synonyms: Dermoid cyst.

Definition: Intracranial dermoid.
Prevalence: 0.5-1.9% of all pediatric brain tumors. M5-10:F1

Etiology: Embryonic cells that fail to differentiate or migrate.
Pathogenesis: Tumors derived from all three embryonic layers.
Associated anomalies: Anen­ce­phaly, facial clefts.
Differential diagnosis: see Table 1.
Prognosis: Usually fatal.
Recurrence risk: Not increased.
Management: Pregnancy termination before viability, conservative management after.

MESH Brain-Neoplasms-diagnosis; -pathology; -embryology; -mortality; Teratoma-diagnosis; -pathology; -embryology; -mortality; Hydrocephalus-diagnosis BDE 2919 MIM 27312, 27330, ICD9 225.0 CDC 742.900 238.010

* Address correspondence to Tae-Hee Kwon, MD, Visiting Fellow, Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 21st and Garland Ave, Nashville, TN 37232-2675. Ph 615-322-0999 Fax 615-322-3764

Introduction

Although fetal head enlargement is most commonly secondary to hydrocephalus, other etiologies including tumors must be considered. Congenital intracranial teratomas are extremely rare tumors. These are usually diagnosed after birth, but prenatal ultrasound detection has been reported^1-4. We wish to add another case of prenatal diagnosis of intracranial teratoma.

Case report

A 26-year-old white woman, gravida 1, para 1, was referred for routine second trimester ultra­sound examination. The pregnancy had been uncomplicated, with the exception of first trimester bleeding which resolved spontaneously.

This male fetus was 28 weeks old by long bone measurements. The fetal head was grossly enlar­ged, with the BPD measuring approximately 120 mm, rather than the expected 73 mm. The brain was largely replaced by a complex mass that contained calcifications (fig. 1).

Fig. 1: Large cystic lesions are present peripherally, corresponding to hydrocephaly due to central obstruction of the region of thalamus by a hyperechoic mass.

Large cystic regions were present peripherally, corresponding to hydrocephaly due to central obstruction. Color Doppler demon­stra­ted few vessels. Other findings were unremarkable.

Due to the poor prognosis of the lesion, termination of pregnancy was performed. A stillborn male fetus weighing 2,040g was delivered. At autopsy, marked enlargement of the head was present and cranial sutures were widely splayed. On gross pathologic examination, the brain weighed 410g, the cerebral hemispheres were spread widely apart by a central heterogeneous mass measuring 8.5 x 5.0 x 5.0 cm. There were 30 cc of bloody serous subdural fluid present.

On formalin fixed brain, the cerebral hemispheres had been dis­placed laterally by a large midline mass. The cerebellum and midbrain had also been displaced anteriorly and inferiorly. The effect of the mass could be seen best in the ventricles, where there was massive hydrocephalus with severe cortical thinning. The size of the mass and its resulting distortion of the normal brain precluded accurate identification of the origin of this mass, but it appeared to be in the posterior midline.

Microscopic examination revealed a predominance of small, round, dark blue nucleus with scant cytoplasm. In addition, other immature cells were seen, including ependyma, lung, intestine, apocrine glands, cartilage, skin and striat­ed muscles. No prominent calci­fication was seen. All of the cells in these different tissues appeared benign.

No site of origin was identified in this case due to the large size of the mass. However, the pineal gland was not identified grossly or microscopically and could be the site of origin in this case. All other organs were normal.

Discussion

Congenital brain tumors represent only 0.5-1.9% of all pediatric brain tumors⁵. Teratoma is the most common tumor in the neonatal period, representing one-third to one-half of all tumors^{5, 6}.

Fetal intracranial tumors are rare, and their incidence is unknown³. The first reported prenatal case appeared in a review of fetal anomalies by Devore and Hobbins in 1979¹. Ten cases of intracranial teratoma have been reported in the literature^1-4.

In a recent study of 45 neonatal brain tumors⁶, the diagnoses were 12 teratomas, 12 primitive neuroectodermal tumors (including 4 me­dulloblastomas), 9 astro­cytomas, 4 glioblastomas multiforme (astro­cytoma grade IV), 3 choroid plexus papillomas and one of each of ependymoma, me­dul­lo­epi­the­lio­ma, germinoma, an­­gioblastic me­ningioma and ganglioglioma. Two-thirds of these tumors were supratentorial, which contrasts with the usual infratentorial location of infantile brain tumors.

Pathology

Teratomas are tumors derived from the three embryonic layers. They may contain well-differentia­ted structures (such as hair, bone, or muscle) or undifferentiated structures. In the latter case, they have a tendency toward malignancy. Teratomas usually oc­cur in the pineal region (2/3), the suprasellar region, or the fourth vent­ricle¹⁰.

Intracranial teratomas are more common in males than females (M5-10:F1)¹⁰. The exceptional fami­lial occurrence of pineal teratomas in two brothers has been reported¹¹.

Diagnosis

The use of ultrasound to assess fetal intracranial structure allows differentiation between tumors, hydrocephalus and other abnormalities³. Experience in the pre­natal diagnosis of brain neoplasm is limited. Cystic tumors and teratomas are usually characterized by complete loss of the normal intracranial architecture⁴. A brain tumor should be suspected when space-occupying lesions with cystic areas and/or solid areas are seen or when there is a change in shape or size of normal anatomic structures. Hydrocephalus is frequen­tly associated with brain tumor and may be the presenting sign⁷.

The intrauterine diagnosis of intra­cranial teratoma by ultra­sound is rare. Early and accurate diagnosis may be important, both in reducing maternal morbidity and in offering appropriate advise to parents with regard to prognosis.

Associated anomalies

Two of the neonatal cases of intra­cranial teratomas had associated congenital anomalies such as an­encephaly and facial cleft¹³, and about half of prenatal cases had polyhydramnios².

Differential diagnosis

The differential diagnosis in infants is relatively limited, usually including astrocytoma, teratoma and ependymoma. Other causes of cystic tumors include hematoma and cystic neoplasm^{8, 9}. Another differential diagnosis includes pinealo­bla­stoma and pa­pillary epen­dy­moma. There are, unfortunately, few distinguishing factors between these different types of tumors, and most present as a large heterogeneous and partially cystic mass with associated hydrocephalus.

Medullo­epith­elio­ma may be hypoechoic, while astro­cytoma, lipoma and angio­blastic menin­gio­ma are hyper­echoic.

Teratomas are usually associated with calcifications. Our case presented with sonographic suggestion of calcifications, but this was not confirmed at pathology.

Intrauterine infections may also produce calcifications, although they are not typically associated with a mass or the distortion of the intracranial structures.

Table 1: Differential diagnosis of cystic teratoma⁶

Prognosis

The prognosis of intracranial tumors depends on a number of factors, including the histologic type, size and location of the lesion. Prenatally diagnosed congenital intracranial teratomas are usually fatal⁷.

In a study of 25 perinatal teratomas¹², 11 were stillborns (group 1), 5 delivered alive but were abnormal at birth (group 2), and 9 were normal at birth but became symptomatic within the first 3 months of life (group 3). The prognosis for the infants in the second group was uniformly fatal within 1 hour to 9 weeks. One of the infants of the third group survived. The first and second groups are most likely to be detected prenatally (mass plus hydrocephalus) and can probably best be used to assess the prognosis in fetuses. Should a small intracranial mass be detected pre­natally, unassociated with hydro­cephaly (thus likely to be equi­valent to group 3), one could expect a small chance of survival (1 in 9), and the lesion should probably be monitored for its growth rate if it is considered in a position that would allow resection. This contrasts with the prognosis in older children and adults in which a rather good prognosis has been described¹⁰.

Management

Pregnancy termination can be offered to the parents before viability. The classic teratoma (with important distortion of the intra­cranial anatomy) should be conservatively managed, because it is associated with a very high death rate. Vaginal delivery is usually recommended. If the tumor is associated with macrocrania, a ce­pha­lo­centesis to overcome fetopelvic disproportion should be considered⁷. Infants suspected of having an intracranial tumor should undergo CT or MRI scanning to better define the characteristics and extent of the tumors⁹.

References

1.DeVore G, Hobbins J. Diagnosis of structural abnormalities in the fetus. Clin Perinatol 1979;6:293.

2.Lipman SP, Pretorius DH, Rumack CM, Manco Johnson ML. Fetal intracranial teratoma: Ultrasound diagnosis of three cases and a review of the literature. Radiology 1985;157:491-494.

3.Hoff NR, Mackay IM. Prenatal ultrasound diagnosis of intracranial teratoma. JCU 1980;8:247-249

4.Kirkinen P, Surano I, Juppila P, et al. Combined use of ultrasound and computed tomography in the evaluation of fetal intracranial abnormality. J Perinat Med 1982;10:257.

5.Wakai S, Arai T, Nagai M. Congenital brain tumors. Surg Neurol 1984 ;21 :597-609.

6.Buetow PC, Smirniotopoulous JG, Done S. Congenital brain tumors: Review of 45 cases. AJR 1990;155:587-593.

7.Romero R, Pilu G, Jeanty J, et al. Prenatal Diagnosis of Congenital Anomalies. Appleton & Lange, Norwalk, Connecticut, 1988.

8.Sauerbrei EE, Cooperberg PL. Cystic tumors of the fetal and neonatal cerebrum: Ultrasound and computed tomographic evaluation. Radiology 1983;147:689.

9.Grant EG, Tessler F, Perrella R. Infant intracranial sonography. Radiol Clin North Am 1988; 26:1105.

10.Russell DS, Rubinstein LJ. Pathology of Tumors of the Nervous System, 5th ed. Williams & Wilkins, Baltimore, 1989.

11.Wakai S, Segawa H, Kitahara S, Asano T. Teratoma in pineal region in two brothers. J Neurosurg 1980;53:238.

12.Greenhouse AH,Neubuerger KT. Intracranial teratoma of newborn. Arch Neurol 1960;3:126-32.

13.Rueda-Pedraza ME, Heifetz SA, Sesterhenn IA, Clark GB. Primary intracranial germ cell tumors in the first two decades of life. Perspect Pediatr Pathol 1987;10:160.