The association between Hairy Cell Leukemia (HCL) and non-tuberculous mycobacterial infections (NTMs) is well described, most notably Mycobacterium kansasii. The exact pathophysiology is not known. We report a case of a 31-year-old male with concomitantly diagnosed HCL and disseminated M kansasii infection who presented with rash, pancytopenia, and bulky axillary lymphadenopathy. The M kansasii was initially diagnosed through use of cell-free DNA detection and confirmed by bone marrow and lymph node cultures. Hairy Cell Leukemia was diagnosed with peripheral flow cytometry and confirmed via the same bone marrow sample. His HCL was put into remission with a single course of cladribine and rituximab chemotherapy; however, his M kansasii infection persisted for 6 months despite aggressive antimicrobial and surgical therapy. It was finally controlled using high-dose rifampin in combination with azithromycin and ethambutol. This case highlights the known link between HCL and M kansasii. Furthermore, it hints at potential causes beyond chemotherapy-induced immunocompromise. Notable possibilities include HCL cells acting as sanctuary sites for M kansasii to evade the immune system, and subclinical M kansasii infections causing NLRP3 inflammasome overactivation to trigger the oncogenic transformation to HCL. More research into the pathophysiologic link between HCL and M kansasii infections would allow for more effective prevention, diagnosis, and treatment of these severe atypical infections which are the major cause of morbidity in the cladribine era of HCL treatment.

BACKGROUND: 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.
OBJECTIVE: The aim is to discuss the clinic-hematological and immunophenotyping findings of three cases of SBLPN.
METHODS: This is a retrospective observational study.
METHODS: 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.
METHODS: 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.

BACKGROUND: Hairy cell leukemia (HCL) is an indolent B-cell lymphoma characterized by a specific genetic mutation, BRAF V600E, which affects the specific morphology and oncogenesis. For HCL, few reports regarding secondary central nervous system involvement (SCNSI) are available. Herein, we present the case of an 80-year-old woman who had a relapse of HCL with SCNSI.
METHODS: The diagnosis of HCL was made in June 2015 after identifying BRAF V600E proteins by immunohistochemical analysis, and the disease was then controlled for 6 years by employing chemoimmunotherapy. In February 2021, the patient was admitted with neurological symptoms such as dizziness. Magnetic resonance imaging of the brain showed abnormal enhancement in the cerebrum, and cerebrospinal fluid analysis revealed neoplastic cells without transformation into large cells. Thus, the patient was diagnosed as having SCNSI in HCL.
CONCLUSIONS: We report a case of a rare clinical presentation of SCNSI in HCL with literature review.

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Mature B-cell lymphoproliferation with hairy lymphocytes include Marginal Zone Splenic Lymphoma (SMZL), Hairy Cell Leukemia (HCL), Splenic Diffuse Red Pulp Lymphoma (SDRPL), and Variant Hairy Cell Leukemia (HCL-v), the two latter being provisional entities that appeared in the 2008 WHO classification. We report the case of a 75-year-old man who benefited from a diagnostic re-evaluation of his SMZL. The good clinical evolution, the flow cytometry investigation (HCL score < 3, SDRPL score > 3, strong CD180 and CD200/CD180 ratio < 0.5) and the histological assessment favored a SDRPL. This entity did not exist at the time of the diagnosis in 2006. The differential diagnosis between these diseases sometimes remains uneasy. Here are mentioned some practical clues to assess the diagnosis.
Les syndromes lymphoprolifératifs B matures avec des lymphocytes d’aspect « chevelus » comprennent le lymphome splénique de la zone marginale splénique (SMZL), la leucémie à tricholeucocytes (HCL), le lymphome diffus de la pulpe rouge (SDRPL) et la leucémie à tricholeucocytes variante (HCL-v), ces deux dernières étant des entités provisoires apparues dans la classification OMS 2008. Nous rapportons le cas d’un homme de 75 ans qui a bénéficié d’une réévaluation diagnostique de son SMZL. En effet, la bonne évolution clinique, les données des explorations par cytométrie en flux (score HCL < score SDRPL > 3, CD180 fort et ratio CD200/CD180 < 0,5) et les données anatomopathologiques ont conclu à un SDRPL. Cette entité n’existait pas lors du diagnostic en 2006. Le diagnostic différentiel entre ces différentes pathologies n’étant pas toujours aisé, nous tenterons de donner quelques pistes pratiques pour conduire au diagnostic précis.

Hairy cell leukemia-Japanese variant (HCL-jv) shares some features with, but differs in other features from, HCL variant. Recently, it has been pointed out that HCL-jv and splenic diffuse red pulp small B-cell lymphoma (SDRPL) possibly constitute the same disease. We report a patient with HCL-jv, in which the neoplastic cells in the resected spleen were positive for CD11c, CD103, tartrate-resistant acid phosphatase (by immunohistochemistry), and weakly positive for cyclin D3. They were negative for CD25, CD123, annexin A1, and BRAF V600E-derived protein. Meta-analysis of HCL-jv cases in the literature showed considerable variation in the expression of HCL-related molecules. Although the clinical features and pattern of splenic involvement of HCL-jv are similar to those of SDRPL, some cytomorphological and phenotypical differences can be pointed out. To confirm whether the weak expression of cyclin D3 in our case suggests a spectrum from HCL-jv to SDRPL or one of the characteristics of HCL-jv, further studies on a large number of cases are necessary.

BACKGROUND: This case report is presented to improve our understanding of the atypical immunophenotype of hairy cell leukemia.
METHODS: A 58-year-old woman presented to our department with fatigue for >10 days.
METHODS: The patient was diagnosed with an increased proportion of abnormal lymphocytes in peripheral blood and bone marrow smear, positive for CD11c, CD19, CD20, CD22, CD25, CD123, CD200, and Kappa, partial expression of CD23, but no expression of CD103, positive for BRAF V600E mutation.
RESULTS: Cladribine combined with rituximab achieved complete remission of minor residual disease negativity.
CONCLUSIONS: Hairy cell leukemia is rare, and the diagnosis and differential diagnosis should be made by combining the patient\'s medical history, clinical manifestations, immunophenotype, gene detection, and other means. Purine nucleoside analogs are the first-line treatments.

Splenic diffuse red pulp small B-cell lymphoma (SDRPL) is a rare disease, representing <1% of all non-Hodgkin lymphomas (NHL). The most common clinical manifestations include splenomegaly, lymphocytosis, and hemocytopenia. A diagnosis of SDRPL can be challenging, as it shares multiple clinical and laboratory features with splenic marginal zone lymphoma (SMZL), hairy cell leukemia (HCL), and HCL variant (HCL-v). Obtaining splenic tissue remains the gold standard for diagnosis. In the cases where splenic tissue is not available, diagnosis can be established by a review of peripheral blood and bone marrow studies. SDRPL is characterized by a diffuse involvement of the splenic red pulp by monomorphous small-to-medium sized mature B lymphocytes effacing the white pulp. The characteristic immunophenotype is positive for CD20, DBA.44 (20 to 90%), and IgG, and typically negative for CD5, CD10, CD23, cyclin D1, CD43, annexin A1, CD11c, CD25, CD123, and CD138. The Ki-67 proliferative index is characteristically low. Cyclin D3 is expressed in the majority of SDRPL in contrast with other types of small B-cell lymphomas, thus facilitating the recognition of this disease. There is no standard treatment regimen for SDRPL. Initial treatment options include splenectomy, rituximab monotherapy, or a combination of both. Chemoimmunotherapy should be considered in patients with advanced disease at baseline or progression.

Hairy cell leukemia variant (HCLv) is a provisional disease in the 2016 WHO classification of lymphomas, characterized by unfavorable prognosis and early relapse following conventional purine analog-based regimens. In this study, we report 2 patients with relapsed HCLv treated with ibrutinib. The first patient achieved a partial response following ibrutinib treatment and received the drug for 16 months, without severe adverse events. However, at disease progression venetoclax was not clinically active. The second patient discontinued the drug early due to intolerance. Ibrutinib was active in our patients with HCLv and deserve further investigations.

UNASSIGNED: The presence of specific chemotherapeutic protocols for hairy cell leukemia (HCL) makes it essential to discriminate this entity from other lymphoproliferative disorders. Hence, awareness of the variations in clinical presentations and immunophenotypic aberrancies is requisite to ensure diagnostic accuracy.
UNASSIGNED: A retrospective study was carried out to analyze the clinical-pathological profile of patients with HCL diagnosed over a period of 81 months (2010-September 2017) in our institute. Flow cytometry was performed in all the patients, and further, BRAFV600E mutation analysis was performed by real-time polymerase chain reaction in a limited number of samples.
UNASSIGNED: A total of 353 lymphoproliferative disorders were assessed during the period, of which 16 (4.5%) were diagnosed as HCL, which included 15 cases of classical HCL and single case of HCL-v. Striking male predominance was noted with a median age of 52 (range 22-90 years). 47% patients presented with pancytopenia, while 20% cases had leukocytosis. Three patients presented with bleeding diathesis in the form of melena and purpuric spots. The absence of splenomegaly was observed in 20% patients (4/15) while 2 (13.3%) cases had lymphadenopathy. Hypocellular marrow was observed in 13% cases. Bright expression of CD20/CD22 along with CD25/CD103/CD123/CD11c was noted in all the patients of classical HCL. Aberrant expression of CD23 and CD5 was seen in 33% ( n =5) and 6.7% ( n =1) cases respectively. CD200 was positive in all the 5/15 cases tested. The case of HCL-v presented with very high leukocyte count and exhibited a CD103/CD11c+ and CD123/CD25- profile. BRAFV600E, mutation was present in all the four patients tested who included patients with a hypocellular marrow and absent splenomegaly.
UNASSIGNED: HCL has characteristic profiles, yet it may exhibit unusual clinical and immunophenotypic presentations. Perspicacious use of flow cytometry and BRAFV600E mutation analysis will aid in the diagnosis in unprecedented cases.