No Loose Ends: A Review of the Pharmacotherapy of Hairy Cell and Hairy Cell Leukemia Variant

Splenic B-cell lymphoma/leukemia with prominent nucleoli: A three-case series of the newly named old entity and review of literature

CONTEXT

Splenic B-cell lymphoma/leukemia with prominent nucleoli (SBLPN) aka hairy cell leukemia variant (HCL-v) is a rare B-cell chronic lymphoproliferative disorder. The main diagnostic challenge is to differentiate SBLPN from Classical hairy cell leukemia (HCL-c), as the former faces inferior responses to therapies and a poor prognosis.

AIMS

The aim is to discuss the clinic-hematological and immunophenotyping findings of three cases of SBLPN.

SETTINGS AND DESIGN

This is a retrospective observational study.

METHODS AND MATERIAL

From the year 2011 to 2021, flow cytometry of all the cases with HCL diagnosis was reviewed, and three cases with negative or dim CD25 and hematological presentation matching with SBLPN were picked up.

STATISTICAL ANALYSIS USED

Descriptive statistics is used.

RESULTS

All the cases were male. The age ranges from 43 to 64 years. Median hemoglobin concentration, total leucocyte count, and platelet count were 8.6 g/dL, 6.9 × 109/L, and 53 × 109/L, respectively. The atypical cells were medium to large. All three showed prominent nucleoli. Bone marrow biopsies showed an interstitial pattern of infiltration in all the cases. The hairy cells were positive for CD20, CD11c, and CD103. CD25 was dim positive in one case. Annexin A1 was negative in all three cases. BRAF V600E mutation analysis was done in one case and turned out negative for the mutation.

CONCLUSIONS

SBLPN is a rare entity, usually on-flow cytometry CD25 negative. However, in dim CD25-positive cases, BRAFV600E mutational analysis helps in discerning SBLPN diagnosis and differentiating it from HCL-c.

Prompt Hematological Recovery in Response to a Combination of Pegylated Interferon α-2a and Rituximab in a Profoundly Immuno-Suppressed Hairy Cell Leukemia Patient with a Mycobacterial Infection at Onset: Benefits and Drawbacks of Rapid Immune Reconstitution

The present paper reports, to the best of our knowledge for the first time, the efficacy and tolerability of the combination of interferon (IFN)α-2a in pegylated formulation and rituximab after a “priming” phase with IFN in the frontline treatment of hairy cell leukemia (HCL) in a profoundly immunosuppressed patient with a Mycobacterium abscessus infection at onset. This immunotherapy combination may represent a potential therapeutic option in patients with active severe infection and for whom the use of purine nucleoside analogues (PNA) is contraindicated. The benefits and drawbacks of remarkably rapid immune reconstitution in the context of opportunistic infections are highlighted as well, as the potentially paradoxical effects of immune recovery as a result of effective immunotherapy strategies, known as immune reconstitution inflammatory syndrome (IRIS), have to be taken into account when dealing with patients with opportunistic infections.

Advances in the Treatment of Hairy Cell Leukemia Variant

OPINION STATEMENT

Hairy cell leukemia variant (HCL-V) is a rare B cell lymphoproliferative disorder with a clinical-pathological distinction from the classic form of hairy cell leukemia (HCL-C). HCL-V is more aggressive in nature, has a higher tendency to be refractory to conventional purine analog pharmacotherapies, and leads to a poorer prognosis. Hence, these differing features bring paramount importance to the diagnosis and management of HCL-V. While there is no genetic mutation diagnostic of HCL-V, genetic profiling efforts have identified potential therapeutic targets (i.e., MAP2K1, KDM6A, CREBBP, ARID1A, CCND3, U2AF1, KMT2C) and yielded prognostic markers (i.e., IGHV4-34 rearrangements). To date, combination chemoimmunotherapies, such as cladribine and rituximab, have shown the best results in HCL-V. Future directions include targeted therapies such as moxetumomab pasudotox, ibrutinib, trametinib, and binimetinib and potentially anti-CD22 chimeric antigen receptor T cell therapy. The purpose of this review is to provide an outline of the diagnostic approach and an update on the therapeutic advancements in HCL-V.

Current and Emerging Therapeutic Options for Hairy Cell Leukemia Variant

Hairy cell leukemia variant (HCL-v) is a rare B-cell lymphoproliferative disorder with distinct immunophenotypic and molecular characteristics when compared to classical hairy cell leukemia (HCL-c). In contrast to the enormous progress in therapeutic options for HCL-c, HCL-v remains a therapeutic challenge due to inferior outcomes with standard chemoimmunotherapy and BCR signaling pathway inhibitors, and due to the fact that HCL-v has limited molecular therapeutic targets. In addition, because of the rarity of the disease, there is a paucity of later phase studies or multicenter trials to guide treatment decisions. In this article, we briefly review the diagnostic criteria and clinical characteristics of HCL-v and present a comprehensive overview of current therapeutic options in HCL-v.