CONGENITAL INTRAVENTRICULAR ATYPICAL MENINGIOMA, WHO GRADE 2 leading to a genetic diagnosis of NF2
Childhood meningiomas are a rare entity accounting for about 1.5% of all pediatric intracranial tumors as compared with adults where they constitute nearly one third of such masses (13). While in adults, meningiomas occur in the ventricular system in only 2% of the cases; the number of ventricular lesions in children is four to ten times higher (5-8). Thus, even though they are rare, pediatric meningiomas often pose a challenge to neurosurgeons. This report provides an interesting case of an unusually large atypical intraventricular meningioma in an infant.
Meningiomas in children are usually associated with NF2 or previous cranial irradiation. Perilongo et al.(10) reported that 23% of patients had evidence of neurofibromatosis II (11).
According to the criteria set by the WHO panel, diagnosis of atypical meningioma should be made when the tumor has an average mitotic rate of >4 per 10 hpf, or has 3 of the following 5 features: tumor necrosis; sheet-like patternless growth; small cells with high nucleocytoplasmic ratio; and hypercellularity. Two types of meningiomas, chordoid and clear cell, typically fit these criteria. In a recent review of 8 cases of childhood meningiomas, 2 were diagnosed as atypical with the youngest patient being 3 years old(1). In general, histopathology in childhood meningiomas shows a preponderance of grade I (>70%), with atypical being 2-4% and grade III as less than 5%. Atypical meningiomas however, have been reported to be as high as 20% in at least one case series (9).
Genetic testing for patients suspected of NF2 follows a sequence beginning with tumor cell DNA analysis in cases such as ours. If tumor cell DNA analysis shows NF2 mutations in both alleles, a study of the patient's constitutional DNA is indicated to look for a germline mutation. Of note is that germline nonsense NF2 mutations, such as seen in our patient, are associated with increased disease severity and an increase in the number of NF2-associated intracranial meningiomas (2). Constitutional nonsense and frameshift NF2 mutations are associated with severe, and missense mutations and somatic mosaicism are associated with mild disease (3,4,12) .
The current case illustrates an unusually large, congenital, intraventricular meningioma of atypical pathology in an infant. Given the age at presentation and the presence of constitutional NF2 mutations, this child is likely to eventually develop the multiple other lesions associated with the syndrome. The patient will, therefore, undergo early hearing testing, routine eye examinations and MRI screening for vestibular, other intracranial and spinal lesions starting at age 5 years (2).
Contributed by Muhammad Omar Chohan MD, Tausif Rehman MD, Rafael Medina-Flores MD, Carol Clericuzio MD, Richard Heideman MD, and Erich Marchand MD