Pilomyxoid astrocytoma of the cerebellar vermis in an elderly patient
A 72-year-old male with a distant history of alcohol abuse presented with approximately 6 months of memory loss, difficulty expressing himself, and a progressively worsening gait. A magnetic resonance imaging (MRI) of the brain revealed a 2.5 × 3.7 × 2.5 cm heterogeneously enhancing cystic mass centered within the cerebellar vermis with mass effect on the fourth ventricle and mild ventriculomegaly [Figure and ] as well as an 8 × 6 × 4 mm satellite lesion within the right superior cerebellar peduncle [Figure and ]. On examination at an outpatient clinic, the patient had a slight expressive aphasia but was otherwise neurologically intact. At that time, the differential diagnosis of the lesion included primary glioma versus metastatic or granulomatous disease and the decision was made for surgical resection of the lesion.\nRoutine preoperative testing found the patient to be in rapid atrial fibrillation and he was sent to the emergency room. While undergoing evaluation of the arrhythmia, his rhythm converted to a junctional bradycardia, necessitating placement of transvenous pacemaker. In the absence of other identifiable etiologies for his sudden bradycardia, his cardiac symptoms were attributed to intracranial hypertension secondary to the obstructive hydrocephalus caused by the vermian lesion. A computed tomography (CT) scan of the head revealed ventriculomegaly but no frank hydrocephalus and the patient was taken to the operating room for placement of a ventriculoperitoneal (VP) shunt. Intraoperatively, he was found to have elevated intracranial pressure. His postoperative course was notable for immediate resolution of the cardiac arrhythmia.\nTwo days following placement of the VP shunt, the patient underwent a suboccipital craniectomy for resection of the cerebellar lesion. Intraoperatively, the lesion was found to be soft and mildly vascular with clean margins relative to the surrounding brain. Pathology specimens were sent for frozen histological analysis and were thought to be most consistent with a diagnosis of glioma. A postoperative MRI revealed a subtotal resection of the lesion. Permanent section of the lesion demonstrated a glial neoplasm composed of astrocytes with elongated, bipolar cytoplasmic processes, forming fascicles and focally, loose perivascular patterns, dispersed within an abundant myxoid background [Figure and ]. The tumor cells had round to irregular, hyperchromatic nuclei, with prominent perinuclear halos infiltrating the molecular layer of the adjacent cerebellar folia. They were strongly immunoreactive for GFAP and WT-1 with a MIB-1 labeling index of greater than 5% [Figure and ]. The lesion was diagnosed as a WHO grade 2 PMA. Postoperatively, the patient did well and was discharged to the inpatient rehabilitation service on postoperative day 4 and discharged home 12 days later with residual dizziness and gait imbalance. Following discharge, the patient refused further medical or surgical treatment. His neurologic status and overall health gradually deteriorated and he expired 11 months after initial symptom presentation and 4 months after surgery.