A Case of Hairy Cell Leukemia Variant: Literature Analysis With Focus on Unmet Needs

Abstract

Hairy cell leukemia variant (HCLv) is a sporadic, B-cell non-Hodgkin lymphoma classified under chronic lymphoproliferative disorders. HCLv usually presents with easy fatigue, dragging pain abdomen, anemia, splenomegaly, hepatomegaly, initially leukocytosis followed by leucopenia, hairy cells in the smear and bone marrow, and an increased risk of infections. There is hypercellular bone marrow, and cytopenias are secondary to hypersplenism. It is essential to differentiate HCL from disorders like classic hairy cell leukemia (HCLc), splenic marginal zone lymphoma, and splenic diffuse red pulp lymphoma, as these are biologically different, with divergent approaches and outcomes. HCLv is poorly responsive or primary refractory to standard purine analogs cladribine or pentostatin. It has lower response rates to even cladribine and rituximab combination, a standard of care for classic HCL with very good response rates. Here, we present a case of an elderly male who presented with splenomegaly and leukocytosis, diagnosed as HCLv, and was treated with a cladribine and rituximab-based regime but showed residual cells in bone marrow on flow cytometry at six months post-treatment. There were no residual cells in peripheral blood in flow cytometry. Various aspects of the disease are discussed here with a detailed literature analysis. There is a definite unmet need for research on better treatment options in HCLv to improve its overall outcome.

Keywords: cladribine; hairy cell leukaemia; hairy cell leukemia variant; lymphoma; massive splenomegaly.

Figure 1. (A) Peripheral smear Leishman staining in 100X magnification showing atypical lymphoid cells with fine hairy processes (blue arrow); (B) bone marrow aspiration Leishman 400X magnification showing hairy cells having round to oval nucleus with moderate pale grey cytoplasm (blue arrow); (C) bone marrow biopsy hematoxylin and eosin (H&E) staining in 100X magnification showing cellular marrow, medium-sized lymphoid cells with oval nuclei, open chromatin, absent nucleoli, and a characteristic serrated cytoplasmic border

Figure 2. (A) Peripheral smear Leishman staining in 10X magnification showing normal leukocyte count and distribution, (B) bone marrow aspiration Leishman 40X magnification showing normal hematopoietic cells and lymphocytes, and (C) bone marrow biopsy post-chemotherapy Leishman H&E 10X magnification showing remission of hairy cell leukemia

Figure 3. (A) Axial plane of CECT abdomen showing the presence of splenomegaly (upward red arrow) and hepatomegaly (downward red arrow) and (B) axial plane of CECT abdomen at six months after treatment showing significant resolution of splenomegaly (upward red arrow) and hepatomegaly (downward red arrow)

CECT: Contrast-enhanced computerized tomography

Figure 4. Bone marrow flow cytometric findings show 0.5% B lymphoid cells with positive expression of B cell markers (CD103, CD11c, and CD20)

Figure 5. Peripheral blood flow cytometric findings identify 21% lymphocytes (16% of total events are T cells, <1% B cells and 4% NK cells), and hairy cell markers are negative

NK: Natural killer