Review Question - QID 213726

A 7-year-old girl is brought to the clinic by her parents due to complaints of several weeks of headaches, vomiting, and general malaise. The patient describes her headaches as “all over her head” and most severe after she wakes up in the morning, with gradual relief accompanied by vomiting throughout the day. Her parents note that her headaches and fatigue have impaired her concentration in school. On physical examination, the patient has an inability to abduct the left eye upon leftward gaze as well as slight unsteadiness in her gait. Head CT imaging is obtained and reveals a mass with cystic and solid components in the cerebellum, highly suggestive of a primary brain tumor. Surgical biopsy is performed to classify the tumor, and histological findings are shown in Figure A. Which of the following is the most likely cause of the patient’s symptoms?