Diagnosis is based on detection of CD4<sup>+</sup> CD56<sup>+</sup>, CD123<sup>high</sup>, TCL-1<sup>+</sup>, and blood dendritic cell antigen-2/CD303<sup>+</sup> blasts, together with the absence of lineage specific antigens on tumour cells. The gene discussed is NCAM1; the disease is neoplasm.