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CD5-negative, CD10-negative low-grade B-cell lymphoproliferative disorders (CD5-CD10-LPD) of the spleen comprise a fascinating group of indolent, neoplastic, mature B-cell proliferations that are essential to accurately identify but can be difficult to diagnose. They comprise the majority of B-cell LPDs primary to the spleen, commonly presenting with splenomegaly and co-involvement of peripheral blood and bone marrow, but with little to no involvement of lymph nodes. Splenic marginal zone lymphoma is one of the prototypical, best studied, and most frequently encountered CD5-CD10-LPD of the spleen and typically involves white pulp. In contrast, hairy cell leukemia, another well-studied CD5-CD10-LPD of the spleen, involves red pulp, as do the two less common entities comprising so-called splenic B-cell lymphoma/leukemia unclassifiable: splenic diffuse red pulp small B-cell lymphoma and hairy cell leukemia variant. Although not always encountered in the spleen, lymphoplasmacytic lymphoma, a B-cell lymphoproliferative disorder consisting of a dual population of both clonal B-cells and plasma cells and the frequent presence of the MYD88 L265P mutation, is another CD5-CD10-LPD that can be seen in the spleen. Distinction of these different entities is possible through careful evaluation of morphologic, immunophenotypic, cytogenetic, and molecular features, as well as peripheral blood and bone marrow specimens. A firm understanding of this group of low-grade B-cell lymphoproliferative disorders is necessary for accurate diagnosis leading to optimal patient management.

Coronavirus disease 2019 (COVID-19) pandemic has been a serious threat and has been reported with different presentations and complications. Older age, along with comorbidities such as diabetes, hypertension, or cardiac disease, increases the risk factors for COVID-19 severity and death [N Engl J Med. 2020;382(18):1708–20 and Lancet Respir Med. 2020 05;8(5):475–81]. It is proposed that cancer patients have a significantly higher incidence of severe incidents including admission to the intensive care unit, the necessity for assisted ventilation, and even death after catching the virus compared with non-cancer patients [Lancet Oncol. 2020;21(3):335–7]. It is also described that cancer patients appear to be twice as likely to contract infection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) [JAMA Oncol. 2020;6(7):1108–10]. Hairy cell leukemia (HCL) is a rare B-cell lymphoproliferative disorder, with patients typically presenting with cytopenias, marked splenomegaly in 80–90% of patients, circulating leukemia cells, bone marrow infiltration and the presence of BRAF V600E somatic mutation [Indian J Hematol Blood Transfus. 2014;30(Suppl 1):413–7]. Leukemic cells classically have central nuclei and abundant cytoplasm with hairy-like projections and express CD11c, CD25, CD103, and CD123 [Indian J Hematol Blood Transfus. 2014;30(Suppl 1):413–7]. Loss of CD123 in HCL has been rarely reported in the literature [Am J Hematol. 2019;94(12):1413–22]. We describe a unique case of a COVID-19-positive male who presented with severe respiratory symptoms, deteriorated quickly, and was intubated. Workup of severe progressive pancytopenia and bone marrow examination revealed HCL without splenomegaly and with atypical unusual loss of CD123. To our knowledge, this is the first case of CD123-negative HCL without splenomegaly associated with COVID-19 infection as the initial presentation.

Abstract Mature lymphoid B‐cell proliferations with hairy cells represent heterogeneous entities where specific diagnosis is difficult but important since it impacts therapeutic management. The clinical cases of variant hairy cell leukemia reported herein illustrate the persistence of a clear interest in the use of splenectomy as a therapeutic alternative. Furthermore, ibrutinib appears to be a promising treatment in patients with relapsed/refractory disease.

A 65-year-old woman presented with easy bruising, left upper quadrant pain, decreased appetite, and weight loss. She had splenomegaly and lymphocytosis (lymphocyte count of 11.6 × 109/l), with remarkably abnormal appearing morphology. Her hemoglobin and platelet counts were normal. Peripheral blood flow cytometry revealed a monoclonal B-cell population expressing CD11c, CD25, CD19, CD20, and CD103. An initial diagnosis of hairy cell leukemia (HCL) was made, and the patient was treated with a standard 5-day course of cladribine. However, her lymphocytosis improved transiently, with a relapse 4 months later. There was no improvement in her splenomegaly. An HCL variant (HCL-v) was considered based on her resistance to treatment with a purine nucleoside analog. A subsequent splenectomy improved symptoms. Two years after, the patient suffered a relapse and underwent 6 cycles of CHOP-R (cyclophosphamide, hydroxydaunomycin, oncovin, prednisone, and rituximab), achieving partial remission. While under observation, she progressed with lymphocytosis 6 months later and was treated with pentostatin. There was no significant improvement in her disease, and she died 8 weeks following treatment initiation. HCL-v is a clinically more aggressive mature B-cell lymphoma than HCL with worse splenomegaly, higher lymphocyte counts, and resistance to typical HCL therapy with purine nucleoside analogs. Early recognition of HCL-v in the history, physical examination, and investigations with morphology and flow cytometry is key to patient management. Further, as in our case of HCL-v, cell morphology can be distinctly atypical, with large nucleoli and extremely convoluted nuclei. The distinction between HCL and HCL-v is important as HCL-v patients require more aggressive therapy and closer follow-up.

We describe an application of a cell-binding microarray – to parallel study of morphology, tartrate-resistant acid phosphatase activity and detection of surface markers on peripheral blood lymphocytes of 90 atients with suspected hairy cell leukemia (HCL). We have formulated the microarray-based diagnostic criteria for hairy cell leukemia, hairy cell leukemia variant (HCLv) and splenic marginal zone lymphoma (SMZL). According to these criteria we have suggested the presence of HCL for 55 patients, HCLv – for 7 patients and SMZL – for 10 patients from the studied cohort. These diagnoses were confirmed by standard diagnostic methods in all cases. These results show that the cellbinding microarray can be used in differential diagnosis of HCL, while the high sensitivity of the microarray permits to detect the leukemic cells in spite of leukopenia and low hairy cell content.

We describe an application of a cell-binding microarray – to parallel study of morphology, tartrate-resistant acid phosphatase activity and detection of surface markers on peripheral blood lymphocytes of 90 atients with suspected hairy cell leukemia (HCL). We have formulated the microarray-based diagnostic criteria for hairy cell leukemia, hairy cell leukemia variant (HCLv) and splenic marginal zone lymphoma (SMZL). According to these criteria we have suggested the presence of HCL for 55 patients, HCLv – for 7 patients and SMZL – for 10 patients from the studied cohort. These diagnoses were confirmed by standard diagnostic methods in all cases. These results show that the cellbinding microarray can be used in differential diagnosis of HCL, while the high sensitivity of the microarray permits to detect the leukemic cells in spite of leukopenia and low hairy cell content.

ABSTRACT The aim of the article is to present a rare case of Hairy cell leukaemia variant (HCl-V) which is a distinct clinico-pathological entity with intermediate features between classical HCl (HCl-C) and B-cell prolymphocytic leukaemia. It is an uncommon disorder accounting for approximately 0.4% of chronic lymphoid malignancies and 10% of all HCl cases. A 58 year old woman presented with pain abdomen and loss of weight. On examination she had massive splenomegaly. Peripheral smear was reported as chronic lymphoproliferative disorder (? Hairy cell leukemia or splenic lymphoma with villous lymphocytes). On Bone marrow examination, differential diagnosis was given as splenic lymphoma with villous lymphocytes (SLVL) and prolymphocytic variant of Hairy cell leukemia. On flow cytometric analysis, these cells were positive for CD11c, CD19, CD20, and CD22. Based on the clinical, peripheral smear, bone marrow and flow cytometry findings, a diagnosis of hairy cell leukaemia variant was confirmed. The differential diagnosis should always include SLVL, HCL-C and Japanese variant HCL because they have different clinical and biological features, particularly regarding their response to purine analogue-based treatment or splenectomy.