Massive mature cystic teratoma of the head and neck, masquerading as a glial choristoma, causing respiratory compromise of a neonate

Discussion

The terms ‘choristoma’ or ‘heterotopia’ most accurately describe the congenital malformation of microscopically normal tissue occurring in an abnormal location.6 A glial choristoma is not neoplastic in nature as it grows alongside the surrounding tissue in an expansive manner without infiltrating it.6 These occur mainly in the head and neck region,4 and contain heterotopic neural tissue.1 Glial choristoma refers to ectopic central nervous tissue which is not continuous with the brain.5 This should be differentiated from a hamartoma, which refers to a tumour consisting of an overgrowth of mature normal cells occurring where these cells are usually located.10

Glial choristomas are rare congenital malformations found primarily in neonates and young children. Approximately 250 cases affecting the nasal area and 33 cases affecting the oral cavity have been described in the literature.3 4 No previous cases have been described in the Eastern Cape, South Africa. Within the oral cavity, the tongue is most commonly involved, followed by the palatopharyngeal complex.3–7 11 12 Few cases have been described which involve the infratemporal fossa. Of note, a high percentage (estimated 35%) of oropharyngeal glial choristomas are associated with cleft palate.6

Two major theories regarding the pathogenesis of glial choristoma have been described. The first suggests that nasal and palatopharyngeal glial choristomas develop as a result of herniation of neural glial tissue from the developing brain due to failed embryonic development of the bony cranium.3 5 6 10 The presence of a fibrous stalk connecting some nasal choristomas with intracranial contents supports this theory.6 The second theory suggests that glial choristomas of the tongue develop from abnormal migration of pluripotent cells from the developing neural tube, which become integrated with the myogenic precursors from the occipital somites which migrate to the developing tongue to give rise to lingual muscle.3 5 6 10

Of note, there is no documented relationship between HIV infection and congenital choristoma. HIV is known to be associated with an increased risk of developing certain cancers such as Kaposi sarcoma, non-Hodgkin’s lymphoma, oral cancers and cervical cancer which is thought to be due to altered immune modulation.13 The possibility of association between congenital choristoma occurrence and HIV exposure is an area in which research is currently lacking.

Diagnosis of glial heterotopia can be supported with imaging such as ultrasound, CT and MRI.2 6 14 MRI is superior in evaluating soft tissue involvement within the oral cavity and oropharynx, although both CT and MRI are used in assessing the extent of the lesion, as well as its vascularity when contrast enhancement is used.2 6 In our case, the ultrasound was not of particular diagnostic value; however, the MRI detailed the soft tissue involvement of the mass, its rich vascular supply and confirmed that there was no intracranial continuity. Definitive diagnosis requires histopathological examination. Microscopic examination confirms mature glial tissue (primarily astrocytes) within a fibrovascular stroma.2 3 6 11 Less frequently, there may be oligodendrocytes, choroid plexus, neurons and meningeal components seen, as in our case.2 6 These lesions are immunocytochemically reactive to GFAP and S-100 protein.2 3 6 11 There have also been cases described with reactions to anti-neuron-specific enolase antibodies and neurofilament stains.2 6 11

A mature cystic teratoma is a rare benign congenital growth comprising cells from all three germ layers.8 9 Within the oral cavity and oropharynx the incidence is 1 in 35 000–200 000 000 live births.9 When protruding from the oral cavity or face, they should be identifiable during antenatal sonography as early as 15–16 weeks of gestation.9 15 There are cases described where diagnosis using antenatal ultrasound is only made in the third trimester which may be due to progressive growth in mass size during gestation.15 In cases associated with polyhydramnios, there should be a high suspicion for airway compromise and appropriate planning for airway management immediately after delivery should be made.9 In this case the growth was unfortunately not identified during the antenatal period. This may have been due to the mass being too small to identify at the time of antenatal ultrasound.

MRI findings for a teratoma are non-specific, and definitive diagnosis is made on histology.8 As a biopsy is only a representative of part of a mass, it is possible that tissue from only one germ cell layer is identified during biopsy, as was seen in this case, and an incorrect diagnosis is made without complete surgical resection. This highlights the importance of sending full tumour resections for histology even when a biopsy diagnosis exists prior to surgery.

As both glial choristomas and mature cystic teratomas are benign conditions, the treatment of choice is complete surgical excision, which is curative.2 3 6 Recurrence may occur if excision is incomplete.2 3 However, the site or extent of these lesions is not always amenable to single stage excision and may require a staged-resection approach with input from numerous surgical disciplines.14 Palatoplasty and maxillofacial reconstruction may be needed post surgical excision of glial heterotopia occurring in the oral cavity and parapharyngeal region, as is the case with our patient.

When occurring in the upper aerodigestive tract, oral cavity or deep neck spaces, these growths have the potential risk for upper airway compromise requiring surgical intervention. This is of importance in the paediatric population where tracheostomy insertion is more technically challenging and associated with higher morbidity and mortality rates.16 17 Residing far from the hospital is a known risk factor for increased mortality from a paediatric tracheostomy, which is of significant concern in our setting. The majority of tracheostomy-associated morbidity and mortality results from granuloma, infection, cannula obstruction and accidental decannulation.16 17 Because of this, definitive treatment of both glial choristoma and teratoma is needed to reduce the morbidity and mortality associated with paediatric tracheostomy. In our case, for example, the neonate requires in-patient tracheostomy care with regular suctioning and respiratory support which the family is unable to provide at home due to financial constraints, electricity supply concerns and distance to appropriate medical care.