B-cell prolymphocytic leukemia | |
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Prolymphocyte | |
Specialty | Hematology, oncology |
B-cell prolymphocytic leukemia, referred to as B-PLL, is a rare blood cancer. It is a more aggressive, but still treatable, form of leukemia.
Specifically, B-PLL is a prolymphocytic leukemia (PLL) that affects prolymphocytes – immature forms of B-lymphocytes and T-lymphocytes – in the peripheral blood, bone marrow, and spleen. It is an aggressive cancer that presents poor response to treatment. [1]
Mature lymphocytes are infection-fighting immune system cells. B-lymphocytes have two responsibilities: [2]
It is categorized as a lymphoproliferative disorder due to the excessive production of lymphocytes, in B-PLL there is excess production of B-prolymphocytes by the bone marrow. These immature lymphocytes are not normally found in the blood; part of their maturation process is being programmed to produce antibodies against foreign material prior to their departure from the bone marrow. [3]
It has been suggested that some cases may represent a variant of mantle cell lymphoma. [4]
This type of leukemia is characterized by: [5] [6]
Similar to other leukemias, B-cell prolymphocytic leukemia is often asymptomatic. The most common signs and symptoms are the result of the inability of the bone marrow to produce normal levels of blood cells: [7]
Diagnosis of B-PLL is difficult due to its considerable overlap with other mature B-cell leukemias and lymphomas. [8] It requires integration of morphology with diagnostic tests including immunophenotyping and chromosome analysis (cytogenetics).
The malignant B cells are larger than average.
In order to diagnose a patient with B-PLL, b-prolymphocyte composition of a patient's blood cells must exceed 55%. High white blood cell counts – greater than 100 x 109/L [8] – are also indicative of B-PLL. B-prolymphocytes are characterized by: [8] [9] [10]
This technique is used to study proteins expressed in cells using immunologic markers. In B-PLL patients there is strong expression of surface immunoglobulin – a membrane-bound form of an antibody, b-lymphocyte surface antigens CD19, CD20, CD22, CD79a and FMC7, and weak expression of CD5 and CD23. [11] Due to the similarities among lymphoproliferative disorders, it is often difficult to diagnose patients. Immunophenotyping helps distinguish B-PLL from similar diseases, one of its key identifiers is the absence in expression of the surface antigens CD10, CD11c, CD25, CD103 and cyclin D1 – an important regulator of cell-cycle progression. [5]
A case has been described as CD20+, CD22+, and CD5-. [12]
It can also be CD5+. [13]
Another case was described as CD45+, CD19+, CD20+, CD5+, HLA-DR+, CD10-, CD23+/-, CD38+ and FMC7-. [14]
B-PLL is rare, consequently few genetic studies have focused on this disease. As a result, the associated genetic lesions underlying B-PLL are largely unknown.
The most commonly reported abnormalities have occurred at chromosome 14, specifically in a region of the chromosome called band q23 (14q23). Translocations to this location lead to overexpression of the cyclin D1 gene [11] which has been linked to both the development and progression of a number of cancers. [15] Other chromosomal abnormalities have been reported on 6q21, 11q23, 12p12, 13q14 and 17p. [11]
It can involve deletions from chromosome 11 and chromosome 13. [16]
Among the documented studies, mutations to the TP53 gene have occurred in 75% of all cases of B-PLL. This is the highest incidence among all sub-types of B-cell malignancies. Mutations to this gene have also been documented in other hematologic malignancies. [17]
TP53 is an important transcriptional activator of genes involved in the regulation of the G1 checkpoint of the cell cycle as well as certain genes responsible for programmed-cell death (apoptosis). It is believed that mutations to TP53 are responsible for the frequent therapy resistance and aggressive course of this disease. [17]
In a small number of B-PLL cases, abnormalities in the c-MYC gene have been observed. It is considered a global amplifier and influences nearly all aspects of cellular activity. Among the number of genes it regulates, most are involved in cell growth, cell cycle progression, protein biosynthesis and apoptosis. Amplification of c-MYC has been reported in B-PLL patients and while the consequences are unclear, it is generally associated with poor clinical outcome. [18]
After physicians have identified an abnormality in the composition of the peripheral blood, biopsies (tissue samples) from a patient's bone marrow and/or spleen are often recommended for confirmation. A bone marrow biopsy involves the removal of a small amount of tissue that is further analyzed for abnormalities, [19] for B-PLL pathologists look for prolymphocytic infiltration where the hematopoietic stem cells of the bone marrow are replaced with prolymphocytes due to excess production. In 50% of reported cases, it was common for patients to be both anemic (lack healthy red blood cells in blood) and thrombocytopenic (deficiency of platelets in blood). [20]
The rarity of B-PLL paired with its considerably fast progression compared to other leukemias has resulted in difficult production of effective treatments. This disease is currently incurable, treatments and therapy are guided to reduce prolymphocyte abundance in the blood and production by the bone marrow, treating symptoms and controlling progression. [20]
Some patients do not require immediate treatment after diagnosis; these patients include those that do not show overt symptoms or whose cancer has not been observed to be progressing. Regular check-ups with physicians are required to actively monitor the patient's condition; once there is evidence of disease progression or patient distress from symptoms, treatment will be implemented. [7] [21]
B-PLL has a very aggressive clinical course and refractoriness to chemotherapy; [8] it is believed this resistance is the result of mutations to the TP53 gene. Its resistant nature has led to the use of combinations of chemotherapy drugs. Drug regimens recommended and employed by physicians are unique to each patient and are based on previous chemotherapy experience along with potential side effects. In addition to the utilization of combinations of chemotherapeutic drugs, it is most often paired with immunotherapy treatments. [8]
A type of targeted therapy that recognizes specific proteins in leukemia cells preventing collateral damage to normal, healthy cells. [19] The following are compounds currently showing promising results in clinical trials and studies:
Ibrutinib is a targeted therapy known as a Bruton's tyrosine kinase (BTK) inhibitor. It works by interfering with signaling pathways that promote the survival and proliferation of B-cells, including malignant B-cells in B-cell prolymphocytic leukemia (B-PLL). [22] Recent observational studies have demonstrated that ibrutinib-containing regimens can be effective in treating B-cell prolymphocytic leukemia (B-PLL), specifically improving progression-free survival (PFS) and potentially overall survival (OS) compared to historical data for B-PLL. [23]
Patients with splenomegaly (enlarged spleen), unfit for systemic treatment or refractive to chemotherapy may have their spleens removed via splenectomy or undergo splenic irradiation in order to relieve pain, control their symptoms, and allow removal of a major proliferative focus and tumour bulk in this disease. [8] [21]
Splenic irradiation has been used in the treatment. [24]
A stem cell transplant is a procedure that uses highly specialized cells called hematopoietic stem cells to replace bone marrow that contains the leukemia. This procedure should be considered in younger patients that have responded well to initial treatments because the progression and spread of this disease is inevitable. [8] However, stem cell transplantation is a high-risk procedure, with significant morbidity and mortality rates. Furthermore, it is often not a feasible option due to the presence of other systemic diseases/conditions. [8] [19]
Despite advancements in treatments and deeper understanding of pathogenesis, the prognosis for B-PLL patients is poor, [25] with early relapse and median survival time between 3–5 years. [26] [27]
B-PLL represents less than 1% of all leukemia cases worldwide, [28] mainly affecting the elderly population with a mean age of presentation between 65 and 70 [29] years. Most cases have shown slight male predominance, with a male-to-female ratio of 1.6 to 1, [28] and the vast majority of patients being Caucasians. [5]
Leukemia is a group of blood cancers that usually begin in the bone marrow and produce high numbers of abnormal blood cells. These blood cells are not fully developed and are called blasts or leukemia cells. Symptoms may include bleeding and bruising, bone pain, fatigue, fever, and an increased risk of infections. These symptoms occur due to a lack of normal blood cells. Diagnosis is typically made by blood tests or bone marrow biopsy.
Chronic lymphocytic leukemia (CLL) is a type of cancer in which the bone marrow makes too many lymphocytes. Early on, there are typically no symptoms. Later, non-painful lymph node swelling, feeling tired, fever, night sweats, or weight loss for no clear reason may occur. Enlargement of the spleen and low red blood cells (anemia) may also occur. It typically worsens gradually over years.
Chronic myelogenous leukemia (CML), also known as chronic myeloid leukemia, is a cancer of the white blood cells. It is a form of leukemia characterized by the increased and unregulated growth of myeloid cells in the bone marrow and the accumulation of these cells in the blood. CML is a clonal bone marrow stem cell disorder in which a proliferation of mature granulocytes and their precursors is found; characteristic increase in basophils is clinically relevant. It is a type of myeloproliferative neoplasm associated with a characteristic chromosomal translocation called the Philadelphia chromosome.
Tumors of the hematopoietic and lymphoid tissues or tumours of the haematopoietic and lymphoid tissues are tumors that affect the blood, bone marrow, lymph, and lymphatic system. Because these tissues are all intimately connected through both the circulatory system and the immune system, a disease affecting one will often affect the others as well, making aplasia, myeloproliferation and lymphoproliferation closely related and often overlapping problems. While uncommon in solid tumors, chromosomal translocations are a common cause of these diseases. This commonly leads to a different approach in diagnosis and treatment of hematological malignancies. Hematological malignancies are malignant neoplasms ("cancer"), and they are generally treated by specialists in hematology and/or oncology. In some centers "hematology/oncology" is a single subspecialty of internal medicine while in others they are considered separate divisions. Not all hematological disorders are malignant ("cancerous"); these other blood conditions may also be managed by a hematologist.
Acute lymphoblastic leukemia (ALL) is a cancer of the lymphoid line of blood cells characterized by the development of large numbers of immature lymphocytes. Symptoms may include feeling tired, pale skin color, fever, easy bleeding or bruising, enlarged lymph nodes, or bone pain. As an acute leukemia, ALL progresses rapidly and is typically fatal within weeks or months if left untreated.
Hairy cell leukemia is an uncommon hematological malignancy characterized by an accumulation of abnormal B lymphocytes. The incidence of hairy cell leukemia (HCL) is 0.28-0.30 cases per 100,000 people in Europe and the United States and the prevalence is 3 cases per 100,000 in Europe with a lower prevalence in Asia, Africa and the Middle East.
Waldenström macroglobulinemia is a type of cancer affecting two types of B cells: lymphoplasmacytoid cells and plasma cells. Both cell types are white blood cells. It is characterized by having high levels of a circulating antibody, immunoglobulin M (IgM), which is made and secreted by the cells involved in the disease. Waldenström macroglobulinemia is an "indolent lymphoma" and a type of lymphoproliferative disease which shares clinical characteristics with the indolent non-Hodgkin lymphomas. It is commonly classified as a form of plasma cell dyscrasia, similar to other plasma cell dyscrasias that, for example, lead to multiple myeloma. Waldenström macroglobulinemia is commonly preceded by two clinically asymptomatic but progressively more pre-malignant phases, IgM monoclonal gammopathy of undetermined significance and smoldering Waldenström macroglobulinemia. The Waldenström macroglobulinemia spectrum of dysplasias differs from other spectrums of plasma cell dyscrasias in that it involves not only aberrant plasma cells but also aberrant lymphoplasmacytoid cells and that it involves IgM while other plasma dyscrasias involve other antibody isoforms.
Follicular lymphoma (FL) is a cancer that involves certain types of white blood cells known as lymphocytes. The cancer originates from the uncontrolled division of specific types of B-cells known as centrocytes and centroblasts. These cells normally occupy the follicles in the germinal centers of lymphoid tissues such as lymph nodes. The cancerous cells in FL typically form follicular or follicle-like structures in the tissues they invade. These structures are usually the dominant histological feature of this cancer.
Acute myeloid leukemia (AML) is a cancer of the myeloid line of blood cells, characterized by the rapid growth of abnormal cells that build up in the bone marrow and blood and interfere with normal blood cell production. Symptoms may include feeling tired, shortness of breath, easy bruising and bleeding, and increased risk of infection. Occasionally, spread may occur to the brain, skin, or gums. As an acute leukemia, AML progresses rapidly, and is typically fatal within weeks or months if left untreated.
B-lymphocyte antigen CD20 or CD20 is B lymphocyte cell-surface molecule.
T-cell-prolymphocytic leukemia (T-PLL) is a mature T-cell leukemia with aggressive behavior and predilection for blood, bone marrow, lymph nodes, liver, spleen, and skin involvement. T-PLL is a very rare leukemia, primarily affecting adults over the age of 30. It represents 2% of all small lymphocytic leukemias in adults. Other names include T-cell chronic lymphocytic leukemia, "knobby" type of T-cell leukemia, and T-prolymphocytic leukemia/T-cell lymphocytic leukemia.
Large granular lymphocytic (LGL) leukemia is a chronic lymphoproliferative disorder that exhibits an unexplained, chronic elevation in large granular lymphocytes (LGLs) in the peripheral blood.
Richter's transformation (RT), also known as Richter's syndrome, is the conversion of chronic lymphocytic leukemia (CLL) or its variant, small lymphocytic lymphoma (SLL), into a new and more aggressively malignant disease. CLL is the circulation of malignant B lymphocytes with or without the infiltration of these cells into lymphatic or other tissues while SLL is the infiltration of these malignant B lymphocytes into lymphatic and/or other tissues with little or no circulation of these cells in the blood. CLL along with its SLL variant are grouped together in the term CLL/SLL.
Acute megakaryoblastic leukemia (AMKL) is life-threatening leukemia in which malignant megakaryoblasts proliferate abnormally and injure various tissues. Megakaryoblasts are the most immature precursor cells in a platelet-forming lineage; they mature to promegakaryocytes and, ultimately, megakaryocytes which cells shed membrane-enclosed particles, i.e. platelets, into the circulation. Platelets are critical for the normal clotting of blood. While malignant megakaryoblasts usually are the predominant proliferating and tissue-damaging cells, their similarly malignant descendants, promegakaryocytes and megakaryocytes, are variable contributors to the malignancy.
In hematology, plasma cell dyscrasias are a spectrum of progressively more severe monoclonal gammopathies in which a clone or multiple clones of pre-malignant or malignant plasma cells over-produce and secrete into the blood stream a myeloma protein, i.e. an abnormal monoclonal antibody or portion thereof. The exception to this rule is the disorder termed non-secretory multiple myeloma; this disorder is a form of plasma cell dyscrasia in which no myeloma protein is detected in serum or urine of individuals who have clear evidence of an increase in clonal bone marrow plasma cells and/or evidence of clonal plasma cell-mediated tissue injury. Here, a clone of plasma cells refers to group of plasma cells that are abnormal in that they have an identical genetic identity and therefore are descendants of a single genetically distinct ancestor cell.
Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy. It was initially regarded as a form of lymphocyte-derived cutaneous lymphoma and alternatively named CD4+CD56+ hematodermic tumor, blastic NK cell lymphoma, and agranular CD4+ NK cell leukemia. Later, however, the disease was determined to be a malignancy of plasmacytoid dendritic cells rather than lymphocytes and therefore termed blastic plasmacytoid dendritic cell neoplasm. In 2016, the World Health Organization designated BPDCN to be in its own separate category within the myeloid class of neoplasms. It is estimated that BPDCN constitutes 0.44% of all hematological malignancies.
Marginal zone lymphomas, also known as marginal zone B-cell lymphomas (MZLs), are a heterogeneous group of lymphomas that derive from the malignant transformation of marginal zone B-cells. Marginal zone B cells are innate lymphoid cells that normally function by rapidly mounting IgM antibody immune responses to antigens such as those presented by infectious agents and damaged tissues. They are lymphocytes of the B-cell line that originate and mature in secondary lymphoid follicles and then move to the marginal zones of mucosa-associated lymphoid tissue (MALT), the spleen, or lymph nodes. Mucosa-associated lymphoid tissue is a diffuse system of small concentrations of lymphoid tissue found in various submucosal membrane sites of the body such as the gastrointestinal tract, mouth, nasal cavity, pharynx, thyroid gland, breast, lung, salivary glands, eye, skin and the human spleen.
Monoclonal B-cell lymphocytosis (MBL) is an asymptomatic condition in which individuals have increased blood levels of particular subtypes of monoclonal lymphocytes. This increase must persist for at least 3 months. The lymphocyte subtypes are B-cells that share certain features with the abnormal clones of lymphocytes that circulate in chronic lymphocytic leukemia/small lymphocyte lymphoma (CLL/SLL) or, less frequently, other types of B-cell malignancies. Some individuals with these circulating B-cells develop CLL/SLL or the lymphoma types indicated by their circulating monoclonal B-cells. Hence, MBL is a premalignant disorder
Lymphocyte-variant hypereosinophilia is a rare disorder in which eosinophilia or hypereosinophilia is caused by an aberrant population of lymphocytes. These aberrant lymphocytes function abnormally by stimulating the proliferation and maturation of bone marrow eosinophil-precursor cells termed colony forming unit-eosinophils or CFU-Eos.
T-cell acute lymphoblastic leukemia (T-ALL) is a type of acute lymphoblastic leukemia characterized by an aggressive malignant neoplasm of the bone marrow. Acute lymphoblastic leukemia (ALL) is a condition, wherein immature white blood cells accumulate in the bone marrow and crowd out normal white blood cells. Accumulation in the liver, spleen, and lymph nodes frequently occurs as well.
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