Review Question - QID 109890

A 3-year-old girl is brought by her mother to her pediatrician. Her mother reports that the child has had frequent headaches over the past month. She has also vomited every day over the past 2 weeks and has been increasingly fatigued to the point that she has been unable to attend preschool. The child was born at 39 weeks gestation and was previously healthy. She was previously able to walk up and down stairs with alternating feet, ride a tricycle, dress herself, and use 3 word sentences in speech. On examination, the child is lethargic and complaining of a holocranial headache. Her pupils are equally round and reactive to light. Cranial nerves II-XII are intact. Strength is 5/5 in the bilateral upper and lower extremities. Results of a brain MRI are shown in Figure A. Which of the following will most likely be seen on biopsy of the lesion?