Test Details: Immunohistochemical testing is carried out on biopsy/resected tissue specimen. This testing helps to identify specific antigens (proteins) within tissue sections utilizing an antigen-specific antibody .Terminal deoxynucleotidyl transferase (TdT) is a DNA nuclear polymerase, catalysing the template-independent polymerization of deoxynucleotidyl triphosphates to double-stranded gene segment DNA. TdT is mainly expressed in precursors of B- and T-lymphocytes. Therefore, antibodies to TdT are specific markers for precursor cell lymphomas of T- and B-cell origin, namely, acute lymphoblastic leukaemia.