A 7-year-old boy presents with progressive ataxia, headache, and vomiting over 3 months. MRI shows a well-circumscribed cystic lesion in the cerebellar hemisphere with an avidly enhancing mural nodule and obstructive hydrocephalus. The structure marked **B** in the diagram is suspected. Which of the following statements best characterizes this tumor and guides management?
A. WHO Grade 3 tumor with poor prognosis despite surgery, necessitating immediate chemotherapy and radiation
B. WHO Grade 4 tumor with median survival <2 years, requiring palliative care and supportive management
C. WHO Grade 1 tumor with excellent prognosis after gross total resection, and the non-enhancing cyst wall typically does not require resection
WHO Grade 2 tumor requiring adjuvant radiation therapy after subtotal resection to prevent recurrence
D.
Explanation
Why option 1 is correct
The structure marked B is a pilocytic astrocytoma (PA), the most common pediatric brain tumor and most common glioma in children. It is classified as WHO Grade 1 — a slow-growing, well-circumscribed tumor with excellent prognosis (>90% 10-year survival) after gross total resection. The classic gross and imaging finding is a cyst with an avidly enhancing mural nodule; the non-enhancing cyst wall typically contains no tumor and does not require resection. This distinction is clinically crucial for surgical planning and avoiding unnecessary tissue removal. (WHO Classification of CNS Tumors 5th ed 2021; Robbins & Cotran Pathology)
Why each distractor is wrong
Option 2 (WHO Grade 2, adjuvant radiation): Pilocytic astrocytoma is WHO Grade 1, not Grade 2. Although mild atypia, mitoses, and vascular hyperplasia may be present histologically, these do NOT indicate higher grade. Radiation is largely avoided in children due to long-term neurocognitive and endocrine sequelae; it is reserved for unresectable or recurrent disease.
Option 3 (WHO Grade 3, poor prognosis): Grade 3 designation applies to diffuse astrocytomas (e.g., anaplastic astrocytoma), not pilocytic astrocytoma. PA has excellent prognosis with gross total resection, not poor prognosis. Chemotherapy is reserved for unresectable or progressive disease, not routine adjuvant therapy.
Option 4 (WHO Grade 4, palliative care): WHO Grade 4 (glioblastoma) is a different entity entirely, seen in older patients, with aggressive behavior and poor prognosis. Pilocytic astrocytoma is Grade 1 and is often curable with surgery alone in children.
High-YieldNEET PG
Pilocytic astrocytoma = WHO Grade 1 + cyst with enhancing mural nodule + excellent prognosis after gross total resection + cyst wall does NOT need resection.
WHO Classification of CNS Tumors 5th ed 2021; Robbins & Cotran Pathology
Practice similar questions
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.
