Mature occipital teratoma in a neonate

Mature occipital teratoma in a neonate 

Teratomas are the commonest type of congenital tumors, often in the dorsal midline, and arise from totipotent germ cells displaced early in embryogenesis. The overall frequency of a teratoma is 1 in 13,000 live births [1]. Commonly occurring in the sacrococcygeal region in neonates, teratomas of the head and neck constitute only 1–3.5% of all cases [2]. Occipital teratoma is even rarer with a few cases reported till date. This report describes a neonate presenting with an occipital mass that was finally diagnosed to be a mature teratoma and discusses its differential diagnosis from the commoner meningoencephalocele.

Case report 

A 48h term male neonate weighing 3.2kg and born by normal vaginal hospital delivery was referred to this centre with a swelling behind the neck. He was born to non-consanguineous parents and antenatal ultrasonography and maternal alphafetoprotein were not done. The general examination was unremarkable. He had a single 7cm×5cm wide based pedunculated occipital mass with a central 3cm×2cm raw area but no recognizable CSF leak (Fig. 1). It was differentially soft and hard at places; the head circumference, fontanels and gross neurological examination were normal. CECT head revealed a focal mixed density and partially calcified extracranial mass lesion in the posterior basiocciput region with an underlying 1cm×1cm occipital bone defect. Although there was no primary intracerebral pathology, he had a colpocephalic skull and a narrow tongue of bridging brain tissue between the cerebellum and the extracranial mass. The lateral ventricles were mildly enlarged and asymmetric; the other ventricles were normal (Fig. 2). A provisional diagnosis of an occipital encephalocele with possible teratomatous components was made. At surgery, the mass was multiseptate, solid-cystic and contained well-formed teeth and bony structures. The mass was excised after division of the narrow communication with the cerebellum. At histopathology, the mass contained an admixture of mature skeletal muscle, glial tissue, stratified squamous, pseudostratified ciliated and mucin secreting epithelium, cartilage, bony trabeculae and hemopoietic elements; hence a final diagnosis of a mature occipital teratoma was made. The neonate made an uneventful recovery; 3 years later, he is asymptomatic and has normal development and anthropometry. The CECT shows no intracranial residua/recurrence or hydrocephalus.

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Fig. 1. Clinical photograph showing the occipital mass with a central raw area.

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Fig. 2. CECT head showing the partially calcified occipital mass with no intracranial extension (A) and an asymmetric lateral ventriculomegaly (B).

Discussion 

Teratomas are the commonest type of congenital midline tumours. During early embryogenesis, primordial germ cells migrating from the yolk sac get trapped within the developing midline structures and evolve into germ cell tumours including teratomas [1]. Willis defined a ‘teratoma’ as a true tumour or neoplasm composed of multiple tissues of a kind foreign to the part in which it arises [3]. Russell and Rubinstein described teratomas as tumours that contain ectodermal, mesodermal and endodermal elements [4]. While a mature teratoma is composed of well-differentiated elements, an immature teratoma contains primitive elements derived from any or all of the three germinal layers. Malignant teratomas harbour malignant elements derived from any of the germinal layers [5].

In children, teratomas commonly occur in the sacrococcygeal region. The retroperitoneum, anterior mediastinum and thymus, neck including pharynx, basicranium, brain and pineal body, orbit, pelvis and spine, gonads and the subcutaneous tissues are other favoured locations [6]. The majority of head and neck teratomas are located in the anterolateral regions; occipitocervical location is rare with less than 10 cases having been reported between 1966 and 2005 [7]. The clinical features and management of cervical teratoma in children have been extensively profiled in literature. However information regarding occipital teratomas is largely gleaned from a few case reports [5], [6], [7], [8], [9].

Besides hemangiomas, lymphatic vascular malformations, lipomas and cutaneous cysts that may feature in the differential diagnosis, occipital teratomas have been mistaken for meningoencephaloceles with/without a CSF leak in the past [7]. Although anecdotal cases of a teratoma within an encephalocele exist [5], it is crucial to distinguish the infinitely commoner pure forms of either as the pathology, management and outcome differ between the two. Though an elevated maternal serum alphafetoprotein may suggest either diagnosis, a meticulous antenatal ultrasound can provide pathoanatomic details to differentiate between the two. We did not have an antenatal diagnosis and the preoperative suspicion of a teratoma was based on the palpatory finding of a heterogenous mass with bony areas and the corroborative findings on the CECT. However a teratoma can even be a soft/firm mass without macroscopic calcified structures. Unlike similar sized occipital teratomas, encephaloceles are associated with microcephaly, type II Arnold Chiari malformation, primary cerebral parenchymal anomalies and significant ventriculomegaly/hydrocephalus. Associated mild vetriculomegaly [7] and secondary cranial vault anomalies in occipital teratomas may make the diagnosis difficult but appropriate imaging (CECT/MR) should resolve the issue. Though the teratoma may not bear any appendage rarely [8], occipital teratoma bearing nails, digits and even fully formed limbs have been reported [6]. The described case had teeth in addition to the bony structures. An intracranial extension is often evident at imaging and at surgery [5]; this may be intradural or extradural. It is imperative that any substantial intracranial extension is summarily removed at the primary surgical procedure with an additional craniectomy if required to avoid residua and recurrences. This case did not require an intracranial exploration as the posterior fossa structures were normal on the CECT. The long term management of an occipital encephalocele with the commonly associated microcephaly mandates a comprehensive spina bifida clinic based multidisciplinary follow up with a close monitoring of motor and cognitive development through childhood and adolescence. In contrast, the management of uncomplicated occipital teratomas without significant intracranial components is simpler and the outcome excellent.

Conclusion 

Neonatal occipital teratomas are rare and can mimic the comparatively commoner meningoencephaloceles. These two entities must be differentiated to tailor the management and achieve optimal outcome. To the best of our knowledge, this is the youngest neonate with a mature occipital teratoma reported in published English literature.