Histiocytic sarcoma is the current term used to describe a spectrum of poorly differentiated, pleomorphic tumours shown to have an immunophenotype consistent with a myeloid dendritic antigen presenting cell origin: CD1+, CD4−, CD11c+, CD11d−, MHC II+, ICAM−1+, and Thy−1± [50]. This evidence concerns the gene ITGAD and histiocytic sarcoma.