The Common Vein Copyright 2010
Definition
A teratoma is a neoplasm which originates from pleuripotent germs cells which can give rise to any type of tissue. They can arise from ectopic germ cell rests outside the gonads with common sites being in the head, mediastinum, and sacrococcygeal regions. When intracranial in location, they can be either intraaxial masses usually within the cerebral hemispheres or extra axial most commonly located in the pineal or suprasellar regions.
Their etiology is unknown at this point.
Pathologically, teratomas may be classified along a spectrum between mature to immature to malignant. Mature teratomas are well differentiated tissues and usually include tissues derived from all three embryonic layers including ectoderm, mesoderm, and endoderm. Occasionally they may contain tissues derived from one germ cell layer but include differing types of cells, for example they may contain only neural and skin elements both of which originate from ectoderm. Immature or malignant teratomas on the other hand have a histologic appearance of undifferentiated tissue resembling fetal tissue. Intraaxial teratomas tend to be histologically less mature than those seen in the pineal location. When located in the pineal region they tend to be encapsulated which is less likely in intraaxial masses.
Clinically, patients with intraaxial teratomas are quite young, usually discovered prenatally up through under a few months of age. They can present during gestation with greater than expected uterine growth due to the large tumor or from polyhydramnios caused by mass effect on the brainstem leading to decreased fetal swallowing. These babies present with difficult delivery or enlarging head size after birth. Extra axial teratomas generally present later in older children or young adults. Pineal region teratomas, as with other pineal region tumors, can result in Paerinauds syndrome or vertical gaze palsy. They can also rupture and result in a chemical meningitis.
On imaging, both CT and MRI can play a role. Teratomas are complex heterogeneous multilocular masses. They may demonstrate mixed density of lipid, CSF, soft tissue, and calcific density. These findings can be seen with the help of both CT and MRI. After contrast administration, the soft tissue components of these tumors may enhance as well as the lining of the cystic components. When seen on prenatal or neonatal ultrasound, these masses appear as complex intracranial masses with mixed echogenicity, often with cystic anechoic components and with hyperechoic likely calcific areas.
Despite the nonaggressive histologic features of intracranial teratomas which present in a neonate, they are typically aggressive with rapid growth and a poor prognosis.
References
Smirniotopoulos JG, Chiechi MV. Teratomas, dermoids, and epidermoids of the head and neck. RadioGraphics 1995; 15:1437-1455
Bruce A. Sandow, Christopher E. Dory, Maria A. Aguiar, and Alfred Z. Abuhamad Best Cases from the AFIP: Congenital Intracranial Teratoma Radiographics July 2004 24:1165-1170