CD68KP1 is the most frequently expressed marker in MS, followed by MPO, CD117, CD99, CD68/PGM1, lysozyme, CD34, terminal deoxynucleotidyl transferase (Tdt), CD56, CD61/linker of activated T lymphocyte/ factor VIIIrelated antigen, CD30, glycophorin A, and CD4. The gene discussed is CD99; the disease is myeloid sarcoma.