[Novelties in the diagnostics and therapy of hairy cell leukemia]. / Új utak a hajas sejtes leukémia és a rokon kórképek diagnosztikájában és kezelésében.

Differential diagnosis of hairy cell leukemia (HCL) and related disorders (hairy cell leukemia variant and splenic marginal zone lymphoma) is of utmost importance since the treatment and prognosis of these lymphomas differ. Since 2011 diagnosis of hairy cell leukemia has been easier because of discovery of the disease defining somatic mutation BRAF V600E mutation, which has been also known as driver mutation in malignant melanoma. The presence of this mutation enabled targeted molecular therapy in HCL as well. As first line therapy purine nucleoside analogues are the gold standard, but refractory/relapsed patient are candidates for targeted BRAF-inhibitor therapy. This manuscript serves as guidance in making diagnosis and standard treatment of HCL, and summarizes newest data about molecular therapy, including our single center experience collected from 75 patients.

Treatment of refractory hairy cell leukemia with a BRAF-inhibitor: lessons to be learnt.

Hairy cell leukemia is a rare chronic lymphoproliferative disorder with indolent but progressive clinical course. Patients require treatment when they have significant cytopenia or recurrent infections. The gold standard treatment are purine nucleoside analogues (cladribine and pentostatine), with these agents the rate of complete remission can approach even 95 %. The differential diagnosis between classical hairy cell leukemia and other, rare splenic lymphomas that can mimic this disease might be really challenging. Splenic lymphoma with villous lymphocytes and other new, provisional WHO entities share some, but not all immunophenotypical features with hairy cell leukemia. The correct diagnosis is of an extreme importance as these entities require different treatment. Thus further investigation in the pathogenesis of hairy cell leukemia is required in order to solve this challenge. Discovery of the BRAF V600E mutation as a disease-defining genetic event in hairy cell leukemia can be helpful in both differential diagnosis and treatment of this disease. We report the case of three hairy cell leukemia patients, whose diagnosis or treatment was based on this newly discovered somatic mutation, but the treatment results and side effects were individual.

Monoclonal antibody HBME-1 reacts with a minor subset of B cells with villous surface and can be useful in the diagnosis of hairy cell leukemia and other indolent lymphoproliferations of villous B lymphocytes.

The Hector Battifora mesothelial epitope-1 (HBME-1) monoclonal antibody has been generated against human mesothelioma cells and recognizes a biochemically unknown membrane epitope. We have accidentally found that the HBME-1 reacts with scattered lymphocytes showing villous surface in hyperplastic lymphoid tissue. To evaluate its reactivity pattern, we have performed a consecutive immunohistochemical study in nonneoplastic bone marrow and lymphoid samples (n = 40), as well as in malignant lymphoproliferations (n = 427), including hairy cell leukemia (HCL) (n = 72), HCL variant (HCL-v) (n = 13), splenic diffuse red pulp small B cell lymphoma (SDRPL) (n = 8), splenic B cell marginal zone lymphoma (SMZL) (n = 59), and splenic B cell lymphoma/leukemia, not further classifiable on bone marrow morphology (SBCL) (n = 37) cases. The staining pattern of HBME-1 was compared to DBA.44. HBME-1(+) villous lymphocytes were constantly detected in low number in nonneoplastic lymphoid tissues. With multicolor immunofluorescence staining, HBME-1(+) lymphocytes showed a CD20(+)/CD79a(+)/IgM(+) B cell phenotype. In B cell lymphoproliferations of villous lymphocytes, HBME-1 reactivity was demonstrated in 96 % of HCL, 39 % of HCL-v, 50 % of SDRPL, 12 % of SMZL, and 19 % of SBCL cases. Nodal and extranodal marginal zone lymphoma cases were positive in 12 % of the cases. A small minority (4 %) of the other B cell lymphomas and no T cell lymphoma revealed tumor cell reactivity with HBME-1. In conclusion, our study has established that HBME-1 reacts with a minor subset of B lymphocytes and a small proportion of B cell lymphomas, which has not been described previously. We suggest that HBME-1 can be a useful marker in the diagnosis of HCL and other indolent lymphoproliferations of villous B lymphocytes.

[Recurrent somatic mutation in hairy cell leukemia]. / Visszatéro szomatikus mutáció hajas sejtes leukémiában.

Hairy cell leukemia is a mature B-cell non-Hogkin lymphoma characterized by unique clinical, morphological and immunhistochemical features. Patients with hairy cell leukemia usually present with splenomegaly, progressive pancytopenia and a relative indolent clinical course. The diagnosis does not always indicate immediate treatment, as treatment depends on the clinical stage of the leukemia. Asymptomatic disease without progression requires a watchful waiting policy, while other categories usually need treatment. The treatment of choice is purine nucleoside analogues (pentostatin, cladribine) which can achieve complete remission even for decades. Interferon and monoclonal CD20 antibodies can also significantly prolong event-free survival. Unfortunately, only the latter two therapies are easily available in Hungary. Splenectomy, which was suggested as first line treatment before the era of purine nucleoside analogues, is only recommended as a last resort. Although hairy cell leukemia is a well-defined lymphoproliferative disease, sometimes it is difficult to differentiate it from other similar entities such as hairy cell leukema variant, splenic marginal zone lymphoma, small lymphocytic lymphoma etc. Making the correct diagnosis is of utmost importance because of the great difference in treatment modalities. Recently, a somatic mutation was found in all analysed hairy cell leukemia samples, but not in other splenic B-cell lymphomas. This article reviews the significance of this observation and presents the different types of methods for the detection of this mutation.

Spontaneous remission in localized diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) is an aggressive neoplastic disease of the lymphatic system, the activated B-cell type of this disease is likely to have a substantially worse prognosis. In this study, we report the favorable outcome of the activated B-cell type of DLBCL, though untreated, 7 years after diagnosis. In 2003, DLBCL localized to the root of tongue was found in the patient complaining of dysphonia and a pharyngeal globus perception but the patient did not agree to get any active hematological treatment. During the following years, the patient did not have any complaints. At the otorhinolaryngological control examination, in 2010, she was complaint-free, had normal laboratory parameters. Moreover a PET-CT scan did not reveal metabolic activity relating to malignancy. The extraordinary disease process can be explained by the spontaneous regression of the activated B-cell type DLBCL. Spontaneous regression of oral lymphoma has been published only exceptionally. To our knowledge, no report of spontaneous regression of activated B-cell type DLBLC has been reported.