This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Acute Lymphoblastic Leukemia, Subject name: Pathology
All of the following are good prognostic factors for pediatric acute lymphoblastic leukemia, except: 
Select and explain. 
A. CNS disease at diagnosis, B. Initial WBC count of 50000/cumm, C. Hyperdiploidy, D. t(12;21)
A: CNS disease at diagnosis
Answer: A: CNS disease at diagnosis 
Explanation: Favorable prognostic markers include Age between 1 and 10 years, A low white cell count at diagnosis, Hyperdiploidy, Trisomy of chromosomes 4, 7, and 10, and the presence of a t(12;21). Several factors are associated with a worse prognosis: Infancy, older age at diagnosis (presentation in adolescence or adulthood) Translocations involving the MLL gene Higher WBC count at diagnosis (peripheral blood blast counts greater than 100,000/cumm) Presence of CNS disease at diagnosis Hypodiploidy