Pilocytic Astrocytoma
This patient has pilocytic astrocytoma, a WHO grade I tumor that characteristically presents in children as a well-circumscribed cerebellar mass with a cystic component and pathognomonic "hair-like" cytoplasmic processes on smear preparation. 1
Clinical and Radiographic Features Supporting This Diagnosis
The constellation of findings in this case creates a highly specific diagnostic pattern:
Age and location: An 8-year-old child with a cerebellar hemisphere mass fits the classic demographic and anatomic distribution of pilocytic astrocytoma, which shows cerebellar predominance in the pediatric population 1, 2
Imaging characteristics: The well-circumscribed mass with cystic component is pathognomonic for pilocytic astrocytoma, which "frequently presents as cystic lesion with contrast-enhancing mural nodule(s)" 1
Pathologic hallmark: The "hair-like cytoplasmic processes" described on smear preparation represent the bipolar pilocytic cells with elongated "hairlike" processes that define this tumor histologically 3
Why Other Options Are Incorrect
Medulloblastoma: While common in the posterior fossa of children, medulloblastomas arise in association with the ventricular system (typically fourth ventricle) rather than the cerebellar hemisphere, appear as solid masses without the characteristic cyst-with-mural-nodule pattern, and show small blue cell morphology rather than hair-like processes 1
Ependymoma: These tumors arise from the floor of the fourth ventricle in the posterior fossa and are associated with the ventricular system, not the cerebellar hemisphere parenchyma 1
Glioblastoma: This is exceptionally rare in children and presents as an infiltrative tumor with ring enhancement, not a well-circumscribed cystic lesion 1
Meningioma: These are dura-based tumors that would not arise within the cerebellar hemisphere parenchyma and are extremely rare in the pediatric population 1
Prognostic Implications
Complete surgical resection alone is curative for pilocytic astrocytoma, with excellent long-term outcomes. 1, 2
Gross total resection results in no recurrence during 10-year follow-up periods, with overall survival rates of 97.6% at 2 years, 94.6% at 5 years, and 94.6% at 10 years 2
Children have better prognosis than adults due to more favorable tumor locations (cerebellar predominance) 2
Radiation therapy is reserved only for cases with residual tumor after incomplete resection and is not routinely required 1, 2
These tumors rarely undergo malignant transformation, distinguishing them from diffuse infiltrative astrocytomas 1, 3