THE VALUE OF IMMUNOHISTOCHEMISTRY
IN THE ASSESSMENT OF BONE MARROW DISORDERS

Attilio Orazi, M.D., FRCPath. and Dennis P. O'Malley, M.D.

CD99 The monoclonal antibody 013 which detects the cell surface glycoprotein p30/32mic2 (CD99) is a frequently used marker for peripheral neuroepithelioma and Ewing's sarcoma. However, since the antibody recognizes a human thymus leukemia antigen and has also been found in immature TdT bone marrow precursors, CD99 can be used to stain TdT positive leukemic cells in tissue sections. We have compared TdT with CD99 and found that the latter may be a useful surrogate marker for TdT. It is however less sensitive than TdT (Robertson et al, 1997). References Dworzak et al: CD99 (MIC2) expression in paediatric B-lineage leukaemia/lymphoma reflects maturation-associated patterns of normal B-lymphopoiesis. Br J Haematol. 1999 Jun;105(3):690-5. Robertson et al: 013 (CD99) positivity in hematologic proliferations correlates with TdT positivity. Mod Pathol. 1997 Apr;10(4):277-82. Soslow et al: MIC2, TdT, bcl-2, and CD34 expression in paraffin-embedded high-grade lymphoma/acute lymphoblastic leukemia distinguishes between distinct clinicopathologic entities. Hum Pathol. 1997; 28:1158-65. Zhang et al: Immunoreactivity of MIC2 (CD99) in acute myelogenous leukemia and related diseases. Mod Pathol. 2000 Apr;13(4):452-8.