EPID-02AN UNUSUAL PEDIATRIC HYPOTHALAMIC PILOCYTIC ASTROCYTOMA

Abstract

BACKGROUND: Hypothalamic/chiasmatic tumors (H/C) constitute 7-10% of pediatric primary CNS tumors and are typically pilocytic astrocytomas. Local extension is seen in 75% of patients but metastatic spinal cord involvement without intracranial dissemination is rare. We describe an unusual multifocal H/C and spinal cord pilocytic astrocytoma in an 8 year old boy. CASE REPORT: The patient was found to have a pineal cyst 1 year prior to diagnosis when he had a CT scan following minor head trauma. Ten months later he presented with lower back pain. MRI (sacrum) showed distortion of L5 nerve roots. Over 3 months his sacral pain worsened and he developed headaches, emesis and gait disturbance. MRI (brain) showed an enhancing hypothalamic mass and hydrocephalus. Spinal cord MRI revealed an intramedullary T2 hyperintense C2-C5 mass, an intramedullary T2 hyperintense focus at T6 and a cystic lesion bordering S1/S2 nerve roots. Spinal cord lesions enhanced less than the hypothalamic lesion. Additional T2 hyperintense foci of uncertain origin were seen in the midbrain tectum, superior cerebellar peduncles and cerebellar hemispheres. Optic chiasm was eccentrically thickened on the right but without abnormal enhancement. CSF was negative for tumor cells and NF1 studies were negative. The hypothalamic and cervical spinal cord lesions were biopsied/debulked respectively. Microscopic examination (both specimens) revealed low-grade astrocytoma without mitotic activity, necrosis or microvascular endothelial proliferation and only occasional Rosenthal fibers (hypothalamic specimen). Immunostain for neurofilament protein (both specimens) suggested an infiltrative growth pattern but IDH-1 immunostain was negative. Both specimens were BRAF(7q34) duplication(+). Ki67 proliferative index was 2-3%. The patient is currently receiving treatment with vincristine/carboplatin with partial improvement of symptoms. CONCLUSION: Since our patient's CSF was negative for tumor cells it is unclear whether this case represents two genetically distinct (multicentric) tumors or a metastatic pilocytic astrocytoma with a hypothalamic or spinal cord primary lesion.