ROR1 and hairy cell leukemia: In the context of cancer, ROR1 protein levels have been extensively reported using flow cytometry (FC) in multiple haematological tumour types, including acute lymphoblastic leukaemia (ALL), chronic lymphocytic leukaemia (CLL), diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), mantle cell lymphoma (MCL), marginal zone lymphoma, and hairy cell leukaemia (HCL) [1, 4–6].