Hairy cell leukemia variant: the importance of differential diagnosis

Hairy cell leukemia is a rare disease comprising about 2% of lymphoid neoplasms.1 This neoplasm can be confused with other hematologic diseases. Therefore, a differential diagnosis must be performed between classic hairy cell leukemia, hairy cell leukemia variant, and splenic marginal zone lymphoma (SMZL).2 According to the World Health Organization (2008), hairy cell leukemia variant was classified as a provisional entity because it has clinical and pathological features that differ from classic hairy cell leukemia.3 Among these aspects are morphological and immunophenotypic variations and resistance to conventional treatment.1 Furthermore, patients with hairy cell leukemia are treated with nucleoside analogs but these drugs have a reduced response in hairy cell leukemia variant and are even ineffective in some cases.3,4 An alternative for these patients is the association of nucleoside analogs with the monoclonal antibody rituximab (anti-CD20).5 Thus, due to differential treatment, the aim of this study was to report a case of hairy cell leukemia variant and cover some aspects related to the differential diagnosis between the classic and variant forms of the disease and SMZL. This study was