FINAL DIAGNOSIS: CONGENITAL CEREBRAL PRIMITIVE NEUROECTODERMAL TUMOR (PNET)
Congenital neoplasms of the central nervous system are rare, although they have been reported since the mid-19th century (1). They represent only 0.5-1.9% of all pediatric brain tumors (2). In recent years, modern imaging studies such as MRI and CT have allowed early diagnosis of this group of brain tumors.
Review of the literature revealed that medulloblastoma to be the most common type of primary CNS tumor in infants and stillborn fetuses (3), although some series have reported teratoma as the predominant tumor in the fetal and perinatal period (4,5,6). Congenital PNETs are rare in the fetal and perinatal period. Most arise from the cerebellar midline, and if large enough, they can extend into the supratentorial compartment (7). The same infratentorial distribution has been reported in older children and with other tumors (8).
Radiologically, the tumors are seen as solid or heterogenous masses with associated hemorrhage and hydrocephalus. Calcification can be identified by CT scan (2). The presence of hyperechoic areas by ultrasound in suggestive of necrosis (7).
The pathologic findings in this case were indicative of a poorly differentiated congenital neoplasm consistent with a PNET, involving lateral ventricles, brain parenchyma, and meninges with extensive hemorrhage. The strong positive immunohistochemical staining for S-100 and focal expression of GFAP and synaptophysin support multipotential differentiation.
This case is unusual in the supratentorial location of the tumor as well as it early detection in utero. The exact site of origin is still unclear due to the extensive destruction of the CNS tissue.
Contributed by CP Molina, MD, H Hawkins, MD, PhD, GCampbell, MD, PhD, T Rowe, MD, M Grafe, MD, PhD