ICD-10-CM > C00-D49 > C81-C96 > C91 > C91.4 C91.4 Hairy cell leukemia Non-Billable/Non-Specific Applicable To Leukemic reticuloendotheliosis Codes C91.40Hairy cell leukemia not having achieved remissionC91.41Hairy cell leukemia, in remissionC91.42Hairy cell leukemia, in relapse