Pathophysiology
Summary
In the pediatric population, CNS tumors primarily manifest infratentorially, a in contrast to adult CNS tumors which frequently present supratentorially. CNS tumors in children present with symptoms such as headaches, seizures, intracranial hypertension—evidenced by nausea, vomiting, and papilledema—and cerebellar manifestations like ataxia & gait disturbances. Risk factors include genetic syndromes like tuberous sclerosis and neurofibromatosis 1, as well as exposure to ionizing radiation.
Pilocytic astrocytomas are the most common pediatric CNS tumor and are named for their ‘hairlike’ projections observed under microscopy. These benign, grade 1 tumors frequently contain activating mutations in the BRAF gene, leading to abnormal cell growth. They are primarily found in the cerebellum and are composed of cells with long ‘hairlike’ processes that contain Rosenthal fibers, which are eosinophilic corkscrew-shaped glial filaments. These tumors stain positively for GFAP, indicating their glial origin.
Medulloblastoma is the most common malignant CNS tumor in children. Medulloblastomas originate in the cerebellum and can extend into the 4th ventricle, inducing intracranial hypertension. Gross pathology displays soft friable tumors with areas of necrosis Histologically, they are characterized by sheets of small blue cells and Homer-Wright rosettes. Medulloblastomas are known to produce ‘drop metastases’ and commonly test positive for synaptophysin and neuron specific enolase.
Ependymomas are CNS tumors that arise from the ependymal cells lining the ventricular system. They most commonly grow from the roof of the 4th ventricle, which can cause intracranial hypertension. These well-circumscribed tumors contain both solid and cystic components. In adults and those with neurofibromatosis type 2, they often localize along the spinal cord. On histology, ependymomas display perivascular pseudorosettes and ependymal rosettes.
Craniopharyngiomas are benign tumors deriving from the remnants of Rathke’s pouch. Craniopharyngiomas are as the most common supratentorial pediatric tumor, exhibiting a combination of solid, cystic, & calcified components.
Lastly, primary CNS germ cell tumors stem from aberrant embryonal cell migration, and are most commonly germinomas. The most common site for primary CNS tumors is the pineal gland, leading to the formation of pinealomas. Notably, pinealomas can precipitate obstructive hydrocephalus, resulting in intracranial hypertension. Pinealomas can also cause Parinaud syndrome due to compression of the tectum & superior colliculi, presenting with the ‘setting sun sign’ (vertical gaze palsy).
Lesson Outline
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FAQs
Pediatric CNS tumors predominantly develop infratentorially, whereas most adult CNS tumors are supratentorial. These tumors manifest symptoms such as headaches, seizures, and intracranial hypertension. Infratentorial tumors in children can lead to cerebellar symptoms like nausea, vomiting, gait disturbances, ataxia, and impaired coordination. Additionally, these tumors can cause obstructive hydrocephalus due to obstruction of the 4th ventricle, further exacerbating intracranial hypertension.
Pilocytic astrocytomas are the most common pediatric CNS tumor and are named for their ‘hairlike’ projections observed under microscopy. These benign, grade 1 tumors often contain activating mutations in the BRAF gene, leading to abnormal cell growth. They are primarily found in the cerebellum and are composed of cells with long ‘hairlike’ processes that contain Rosenthal fibers, which are eosinophilic corkscrew-shaped glial filaments. These tumors stain positively for GFAP, indicating their glial origin.
Medulloblastomas are the most common malignant CNS tumors in children. They originate from cells that are partially differentiated in the neuronal direction, staining positive for synaptophysin and neuron-specific enolase. These tumors are primarily located in the cerebellum and can extend into the 4th ventricle, leading to intracranial hypertension. Histologically, they are composed of sheets of small blue cells and display Homer-Wright rosettes. Medulloblastomas can also produce ‘drop metastases,’ where the CSF contains malignant cells, forming tumor nodules along the spinal cord.
Ependymomas are CNS tumors that arise from the ependymal cells lining the ventricular system. They most commonly grow from the roof of the 4th ventricle, which can cause intracranial hypertension due to obstructive hydrocephalus. These well-circumscribed tumors contain both solid and cystic components. Histologically, ependymomas display perivascular pseudorosettes and ependymal rosettes, where cancer cells cluster in an attempt to form a ventricle.
Craniopharyngiomas are benign tumors that arise from the epithelial remnants of Rathke’s pouch, which ultimately forms the anterior pituitary. They are the most common supratentorial pediatric tumor. These tumors display a combination of solid, cystic, and calcified components. Due to their location, they can cause a range of symptoms, including headaches, visual disturbances, and hormonal imbalances.
Pinealomas are the most common primary CNS germ cell tumor, and arise from abnormal migration of embryonal cells during development. These tumors can lead to obstructive hydrocephalus by impinging on the cerebral aqueduct, causing intracranial hypertension. Pinealomas can also cause Parinaud syndrome due to compression of the tectum and superior colliculi, presenting with the ‘setting sun sign’ (vertical gaze palsy).
