This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Haematology, Subject name: Pathology
A 17-year-old boy presented with TLC of 138 x 109/ L with 80% blasts on the peripheral smear. Chest X-ray demosnstrated a large mediastinal mass. Immunophenotyping of this patient&;s blasts would most likely demonstrate - 
Select and explain. 
A. No surface antigens (null phenotype), B. An immature T cell phenotype (Tdt/D34/CD7 positive), C. Myeloid markers, such as CD 13, CD33 and CD 15, D. B cell markers, such as CD 19, CD20 and CD22
B: An immature T cell phenotype (Tdt/D34/CD7 positive)
Answer: B: An immature T cell phenotype (Tdt/D34/CD7 positive) 
Explanation: The cluster of differentiation (also known ascluster of designation or classification determinant and often abbreted as CD) is a protocol used for the identification and investigation of cell surface molecules providing targets for immunophenotyping of cells.