The designation HCL-v encompasses cases of B chronic lymphoproliferative disorders that resemble classic hairy cell leukaemia
but exhibit variant "cytohaematologic" features (i.e. leukocytosis, presence of monocytes, cells with prominent nucleoli, cells with blastic or convoluted nuclei and/or absence of circumferential shaggy contours), variant immunophenotype (i.e. absence of CD25, annexin-A1, or TRAP) and resistance to conventional HCL therapy (i.e. lack of dramatic response to cladribine). These cases are no longer considered to be biologically related to HCL.