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The Thistle QA CEU No is: MT-2014/004

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DIFFERENTIAL SLIDES LEGEND

CYCLE 45 SLIDE 5 – DECEMBER 2014

HAIRY CELL

Hairy cell leukemia is an uncommon hematological malignancy characterized by an accumulation of abnormal B . It is usually classified as a sub-type of chronic lymphoid leukemia. makes up approximately 2% of all . Hairy cell leukemia was originally described as histiocytic leukemia, malignant reticulosis, or lymphoid myelofibrosis in publications dating back to the 1920s. The disease was formally named leukemic reticuloendotheliosis and its characterization significantly advanced by Bertha Bouroncle and colleagues at The Ohio State University College of Medicine in 1958. Its common name, which was coined in 1966, is derived from the "hairy" appearance of the malignant B cells under a microscope.

Classification When not further specified, the "classic" form is often implied. However, two variants have been described: Hairy cell leukemia-variant, which usually is diagnosed in men, and a Japanese variant which is more easily treated. The non-Japanese variant is more difficult to treat than either 'classic' HCL or the Japanese variant HCL.

Hairy cell leukemia-variant, or HCL-V, is usually described as a prolymphocytic variant of hairy cell leukemia. It was first formally described in 1980 by a paper from the University of Cambridge's Hayhoe lab. About 10% of HCL patients have this variant form of the disease, while classic HCL primarily affects men; HCL-V is more evenly divided between males and females. While the disease can appear at any age, the median age at diagnosis is over 70. Similar to B-cell prolymphocytic leukemia ("B-PLL") in Chronic lymphocytic leukemia, HCL-V is a more aggressive disease. It is less likely to be treated successfully than is classic HCL, and remissions tend to be shorter. Many treatment approaches, such as Interferon-alpha, the combination "CHOP", and common alkylating agents like cyclophosphamide provide very little benefit. Pentostatin and cladribine provide some benefit to many HCL-V patients, but typically induce shorter remission periods and lower response rates than when they are used in classic HCL. More than half of victims respond partially to splenectomy.

In terms of B-cell development, the are less developed than are lymphocytes or plasma cells, but are still more mature than their lymphoblastic precursors. HCL-V differs from classic HCL principally in the following respects:  Higher counts, sometimes exceeding 100 x109/l  A more aggressive course of disease requiring more frequent treatment  Hairy cells with an unusually large nucleolus for their size  Production of little excess fibronectin produced by classic hairy cells; to interfere with bone marrow biopsies  Low or no cell-surface expression of CD25 (also called the Interleukin-2 [IL-2] receptor alpha chain or p55).

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P.O. Box 131375, Bryanston, 2074 Ground Floor, Block 5 Bryanston Gate, Main Road Bryanston, Johannesburg, South Africa www.thistle.co.za Tel: +27 (011) 463-3260 Fax: +27 (011) 463-3036 OR + 27 (0) 86-557-2232 e-mail : [email protected] Diagnosis The diagnosis of HCL may be suggested by abnormal results on a complete blood count (CBC), but additional testing is necessary to confirm the diagnosis. A CBC normally shows low counts for white blood cells, red blood cells and platelets in HCL patients. However, if large numbers of hairy cells are in the blood stream, then normal or even high counts may be found. On physical exam, 80–90% of patients have an enlarged spleen, which can be massive. Leukemic cells may gather in the spleen and cause it to swell; this can have the side effect of making the person feel full even when he or she has not eaten much. This is less likely among patients who are diagnosed at an early stage. Peripheral lymphadenopathy (enlarged lymph nodes) is uncommon (less than 5% of patients), but abdominal lymphadenopathy is a relatively common finding on computed tomography (CT) scans. Patients with a high tumor burden may also have somewhat reduced levels of cholesterol, especially in patients with an enlarged spleen. Cholesterol levels return to more normal values with successful treatment of HCL.

The most important lab finding is the presence of hairy cells in the bloodstream. Hairy cells are abnormal white blood cells with hair-like projections of cytoplasm; they can be seen by examining a blood smear or bone marrow biopsy specimen. Most patients require a bone marrow biopsy for final diagnosis. The bone marrow biopsy is used both to confirm the presence of HCL and also the absence of any additional diseases, such as Splenic marginal zone or B-cell prolymphocytic leukemia. The diagnosis can be confirmed by viewing the cells with a special stain known as TRAP (tartrate resistant acid phosphatase).

Hairy cell leukemia: abnormal B cells look "hairy" under a microscope Trap stain because of radial projections from their surface.

It is also possible to definitively diagnose hairy cell leukemia through on blood or bone marrow. The hairy cells are larger than normal and positive for CD19, CD20, CD22, CD11c, CD25, CD103, and FMC7. (CD103, CD22, and CD11c are strongly expressed.)

Hairy cell leukemia-variant (HCL-V), which shares some characteristics with prolymphocytic leukemia (B- PLL), does not show CD25 (also called the Interleukin-2 receptor, alpha). The presence of additional lymphoproliferative diseases is easily checked during a flow cytometry test, where they characteristically show different results.

The differential diagnoses include: several kinds of anemia, including myelophthisis and aplastic anemia, and most kinds of blood neoplasms, including hypoplastic myelodysplastic syndrome, atypical chronic lymphocytic leukemia, B-cell prolymphocytic leukemia, or idiopathic myelofibrosis.

Pathophysiology Pancytopenia in HCL is caused primarily by marrow failure and splenomegaly. Bone marrow failure is caused by the accumulation of hairy cells and reticulin fibrosis in the bone marrow, as well as by the detrimental effects of dysregulated cytokine production. Splenomegaly reduces blood counts through sequestration, marginalization, and destruction of healthy blood cells inside the spleen. Hairy cells are nearly mature B cells, which are activated clonal cells with signs of VH gene differentiation. They may be related to pre-plasma marginal zone B cells or memory cells. Cytokine production is disturbed in HCL. Hairy cells produce and thrive on TNF-alpha. This cytokine

Thistle QA is a SANAS accredited organisation, No: PTS0001 Accredited to ISO 17043 Certificate available on request or at www.sanas.co.za

P.O. Box 131375, Bryanston, 2074 Ground Floor, Block 5 Bryanston Gate, Main Road Bryanston, Johannesburg, South Africa www.thistle.co.za Tel: +27 (011) 463-3260 Fax: +27 (011) 463-3036 OR + 27 (0) 86-557-2232 e-mail : [email protected] also suppresses normal production of healthy blood cells in the bone marrow. Unlike healthy B cells, hairy cells express and secrete an immune system protein called Interleukin-2 receptor (IL-2R). In HCL-V, only part of this receptor is expressed. As a result, disease status can be monitored by measuring changes in the amount of IL-2R in the blood serum. The level increases as hairy cells proliferate, and decreases when they are killed. Hairy cells respond to normal production of some cytokines by T cells with increased growth. Treatment with Interferon- alpha suppresses the production of this pro-growth cytokine from T cells. A low level of T cells, which is commonly seen after treatment with cladribine or pentostatin, and the consequent reduction of these cytokines, is also associated with reduced levels of hairy cells.

In June 2011, E Tiacci et a discovered that 100% of hairy-cell leukaemia samples analysed had the oncogenic BRAF mutation V600E, and proposed that this is the disease's driver mutation. Until this point, only a few genomic imbalances in the hairy cells, such as trisomy 5 had been found. The expression of genes is also dysregulated in a complex and specific pattern. The cells under express 3p24, 3p21, 3q13.3-q22, 4p16, 11q23, 14q22-q24, 15q21-q22, 15q24-q25, and 17q22-q24 and overexpress 13q31 and Xq13.3-q21. It has not yet been demonstrated that any of these changes have any practical significance to the patient.

Treatment Several treatments are available, and successful control of the disease is common. Not everyone needs treatment. Treatment is usually given when the symptoms of the disease interfere with the patient's everyday life, or when white blood cell or platelet counts decline to dangerously low levels. Not all patients need treatment immediately upon diagnosis, and about 10% of patients will never need treatment.

Follow-up care Despite decade-long remissions and years of living very normal lives after treatment, hairy cell leukemia is officially considered an incurable disease. While survivors of solid tumors are commonly declared to be permanently cured after two, three, or five years, people who have hairy cell leukemia are never considered 'cured'. People in remission need regular follow-up examinations after their treatment is over. Most physicians insist on seeing patients at least once a year for the rest of the patient's life, and getting blood counts about twice a year. Regular follow-up care ensures that patients are carefully monitored, any changes in health are discussed, and new or recurrent cancer can be detected and treated as soon as possible. Between regularly scheduled appointments, people who have hairy cell leukemia should report any health problems, especially viral or bacterial infections, as soon as they appear.

HCL patients are also at a slightly higher than average risk for developing a second kind of cancer, such as colon cancer or lung cancer, at some point during their lives (including before their HCL diagnosis). This appears to relate best to the number of hairy cells, and not to different forms of treatment. On average, patients might reasonably expect to have as much as double the risk of developing another cancer, with a peak about two years after HCL diagnosis and falling steadily after that, assuming that the HCL was successfully treated. Aggressive surveillance and prevention efforts are generally warranted, although the lifetime odds of developing a second cancer after HCL diagnosis are still less than 50%. There is also a higher risk of developing an autoimmune disease. Autoimmune diseases may also go into remission after treatment of HCL.

References 1. http://en.wikipedia.org/wiki/Hairy_cell_leukemia

Questions 1. Discuss the classification of Hairy cell leukemia. 2. Discuss the pathophysiology of Hairy cell leukemia. 3. Discuss the diagnosis of Hairy cell leukaemia.

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